Binder for electrode in lithium secondary cell, electrode manufactured using said binder, and lithium secondary cell in which said electrode is used

ABSTRACT

A binder for an electrode of a lithium secondary battery contains a water dispersion of a polyurethane. The polyurethane has been formed of (A) a polyisocyanate, (B) a compound having two or more active hydrogen groups, (C) a compound having one or more active hydrogen groups and a hydrophilic group, and (D) a chain extending agent. The (B) compound having two or more active hydrogen groups contains an olefinic polyol and/or a carbonate diol having a carbon number between carbonate bond chains of less than 6. The binder has high adhesiveness to a collector, does not cause release in press molding, has high flexibility, and is excellent in bindability and resistance to an electrolytic solution.

TECHNICAL FIELD

The present invention relates to a binder for an electrode of a lithiumsecondary battery, an electrode produced by using the binder, and alithium secondary battery in which the electrode is used.

BACKGROUND ART

Recently, portable electronic devices such as a mobile phone, a notebookpersonal computer, a personal digital assistant (PDA), a video camera,and a digital camera are widely spread. With further requirements insize reduction and weight reduction of such electronic devices, therequirements in size reduction, weight reduction, thickness reduction,and increase of capacity of a battery as a driving power supply arerising, and investigations relating to these problems are activelyproceeding. A lithium secondary battery has high voltage and a favorableenergy density. For this reason, it has been widely used as a powersupply of the portable electronic devices. However, with the requirementof further small-sized and weight-reduced battery along with thedevelopment of small-sized and weight-reduced display industries,further improved battery characteristics such as high drive voltage,prolonged life and high energy density as compared with a conventionallithium secondary battery are required. Furthermore, recently, thedevelopment of a medium-sized or large-sized lithium secondary batteryfor automobile use or for industries is proceeding, and expectation isplaced on the development in the improvement of high capacity and highoutput. Therefore, to satisfy those requirements, efforts for improvingthe performance of various constituent elements of the lithium batteryhas been continued.

Characteristics of a battery are greatly influenced by an electrode, anelectrolyte and other battery materials used. Particularly, in the caseof an electrode, the characteristics are determined by an electrodeactive material, a current collector and a binder imparting adhesiveforce therebetween. For example, an amount and kind of the activematerial used determine an amount of lithium ions that can be bonded tothe active material. Therefore, a higher capacity battery can beobtained as the amount of the active material is large and the activematerial having larger inherent capacity is used. Furthermore, in thecase where the binder has an excellent adhesive force between the activematerials and between the active material and the current collector,electrons and lithium ions smoothly transfer inside of the electrode,and internal resistance of the electrode is decreased. As a result,highly efficient charge and discharge can be realized.

In the case of a high capacity battery, a composite electrode such ascarbon and graphite or carbon and silicon is required as an anode activematerial, and volume expansion and contraction of the active materialgreatly occur during charging and discharging. Therefore, the bindermust have excellent elasticity in addition to excellent adhesive force,and must maintain the inherent adhesive force and restoring forcedespite that the electrode volume repeatedly undergoes considerableexpansion and contraction.

As a binder for obtaining such the electrode, known is one containing afluorine resin such as polytetrafluoroethylene or polyvinylidenefluoride, dissolved in an organic solvent. However, the fluorine resindoes not have sufficiently high adhesiveness to a metal constituting thecurrent collector, and additionally, does not have sufficiently highflexibility. Therefore, particularly, in the case of producing awound-type battery, there are problems that cracks are generated in anelectrode layer obtained and peeling occurs between the electrode layerobtained and a current collector. To maintain sufficient adhesive force,the used amount of the resin must be increased, and therefore sizereduction has its limit. Furthermore, the resin is used as a mixturewith an organic solvent, and therefore there is a disadvantage that theproduction becomes complicated.

On the other hand, a binder containing a styrene-butadiene latex (SBR)is known as one having high adhesiveness to a metal constituting acurrent collector and capable of forming an electrode layer having highflexibility (Patent Documents 1, 2 and 3). However, it has excellentelastic property, but adhesive force is weak, the structure of anelectrode cannot be maintained with repetition of charging anddischarging, and it cannot be said that a life of the battery issufficient.

In recent years, in view of the demand for enhancement of the batterycapacity, there is a tendency that the content of a binder component asa material constituting the electrode layer is decreased, and theelectrode layer is subjected to press molding in the production processof the electrode. In the electrode layer that has a small content of thebinder component, however, the electrode layer is liable to be releasedfrom the collector during the press molding. Therefore, problems arepointed out not only that contamination of the press molding machinewith the electrode substance occurs but also that the electrode isinstalled in a battery in such a state that an electrode layer ispartially released off and thus the reliability of the batteryperformance is deteriorated. Since such problems may become conspicuouswhen a polymer having a low glass transition temperature and hightackiness is used as the binder component, those may be suppressed byusing a latex of which a polymer has a high glass transitiontemperature, for example, equal to or higher than room temperature.However, in the case of using a binder of which a polymer has a highglass transition temperature, the resulting electrode layer has lowflexibility and thus is liable to suffer cracking, so that there arisesproblems that the capacity retention rate of the battery is deterioratedand sufficient charge and discharge cycle characteristics are notobtained.

BACKGROUND ART DOCUMENTS Patent Documents

-   Patent Document 1: JP-A-5-21068-   Patent Document 2: JP-A-11-7948-   Patent Document 3: JP-A-2001-210318

SUMMARY OF THE INVENTION Problems that the Invention is to Solve

The present invention has been made under the above circumstances, andan object thereof is to provide a binder that has high adhesiveness to acollector, does not cause release in press molding, has highflexibility, and is excellent in bindability and resistance to anelectrolytic solution, and a lithium secondary battery excellent incharge and discharge characteristics in which an electrode produced byusing the binder is used.

Means for Solving the Problems

In order to achieve the object, the present inventors have conductedextensive studies for obtaining a binder that has high adhesiveness to acollector, does not cause release in press molding, has highflexibility, and is excellent in bindability and resistance to anelectrolytic solution. As a result, they have found that, in a binderfor an electrode of a lithium secondary battery, containing a waterdispersion of a polyurethane formed of (A) a polyisocyanate, (B) acompound having two or more active hydrogen groups, (C) a compoundhaving one or more active hydrogen groups and a hydrophilic group, and(D) a chain extending agent, the above problems can be solved by the useof a specific compound as the above (B) component. Thus, they haveaccomplished the present invention.

Namely, the binder for an electrode of a lithium secondary battery ofthe present invention is a binder for an electrode of a lithiumsecondary battery, containing a water dispersion of a polyurethaneformed of (A) a polyisocyanate, (B) a compound having two or more activehydrogen groups, (C) a compound having one or more active hydrogengroups and a hydrophilic group, and (D) a chain extending agent, inwhich the (B) compound having two or more active hydrogen groupscontains an olefinic polyol and/or a polycarbonate diol having a carbonnumber between carbonate bond chains of less than 6.

The olefinic polyol contained as the (B) component is preferablycontained in a ratio of 40% by mass or more and 90% by mass or less withrespect to the polyurethane. Moreover, the polycarbonate diol having acarbon number between carbonate bond chains of less than 6, contained asthe (B) component, is preferably contained in a ratio of 50% by mass ormore and 90% by mass or less with respect to the polyurethane.

The polyurethane preferably has a crosslinking density of 0.01 or moreand 0.50 or less per 1,000 molecular weight of the polyurethane.Moreover, the polyurethane preferably has a urethane bond equivalent of200 g/eq or more and 2,000 g/eq or less.

The olefinic polyol contained as the (B) component may be one kind ortwo or more kinds selected from polybutadiene polyol, polyisoprenepolyol, hydrogenated polybutadiene polyol, and hydrogenated polyisoprenepolyol. The (C) compound having one or more active hydrogen groups and ahydrophilic group preferably contains a carboxyl group as thehydrophilic group. The above (A) polyisocyanate preferably contains analicyclic isocyanate and/or an aromatic isocyanate.

The electrode of the present invention is produced by using the binderfor an electrode of a lithium secondary battery and the lithiumsecondary battery of the present invention has the electrode of thepresent invention.

Advantage of the Invention

The binder for an electrode of a lithium secondary battery of thepresent invention has high adhesiveness to a collector, does not causerelease in press molding, has high flexibility, and is excellent inbindability, and becomes also excellent in resistance to an electrolyticsolution in the case where the (B) component is an olefinic polyol. Alithium secondary battery that is excellent in charge and dischargecharacteristics can be obtained by using an electrode in which thebinder is used.

MODES FOR CARRYING OUT THE INVENTION

The following will explain embodiments of the present invention indetail.

The binder for an electrode of a lithium secondary battery of thepresent invention is a binder for an electrode of a lithium secondarybattery, containing a water dispersion of a polyurethane formed of (A) apolyisocyanate, (B) a compound having two or more active hydrogengroups, (C) a compound having one or more active hydrogen groups and ahydrophilic group, and (D) a chain extending agent, in which the (B)compound having two or more active hydrogen groups contains an olefinicpolyol and/or a polycarbonate diol having a carbon number betweencarbonate bond chains of less than 6.

The polyisocyanate as the (A) component is not particularly limited, andpolyisocyanates that are ordinarily used in this field of art can beused. Specifically, there may be mentioned aliphatic polyisocyanates,alicyclic polyisocyanates, aromatic polyisocyanates, and aromaticaliphatic polyisocyanates. As the aliphatic polyisocyanates, there maybe mentioned tetramethylene diisocyanate, dodecamethylene diisocyanate,hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate,2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate,2-methylpentane-1,5-diisocyanate, 3-methylpentane-1,5-diisocyanate, andthe like. As the alicyclic polyisocyanates, there may be mentionedisophorone diisocyanate, hydrogenated xylylene diisocyanate,4,4′-dicyclohexylmethane diisocyanate, 1,4-cyclohexane diisocyanate,methylcyclohexylene diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane,and the like. As the aromatic polyisocyanates, there may be mentionedtolylene diisocyanate, 2,2′-diphenylmethane diisocyanate,2,4′-diphenylmethane diisocyanate, 4,4′-diphenylmethane diisocyanate(MDI), 4,4′-dibenzyl diisocyanate, 1,5-naphthylene diisocyanate,xylylene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylenediisocyanate, and the like. As the aromatic aliphatic polyisocyanates,there may be mentioned a dialkyldiphenylmethane diisocyanate, atetraalkyldiphenylmethane diisocyanate, α,α,α,α-tetramethylxylylenediisocyanate, and the like. There may also be mentioned a dimer, atrimer, or a modified product such as a biuret-modified isocyanate ofthese organic polyisocyanates. These may be used solely or as acombination of two or more kinds thereof.

Among these polyisocyanates, an alicyclic isocyanate and/or an aromaticisocyanate are preferred from the standpoint of the bindability and theresistance to an electrolytic solution, and specifically,4,4′-dicyclohexylmethane diisocyanate, isophorone diisocyanate and1,3-bis(isocyanatomethyl)cyclohexane are preferred. As thepolyisocyanate to be used in combination with the preferable alicyclicand/or aromatic isocyanate, an aliphatic hexamethylene diisocyanate ispreferred from the standpoint of flexibility.

As the olefinic polyol to be used as the (B) component, there may bementioned polyols such as polybutadiene polyol, polyisoprene polyol andpolychloroprene polyol and hydrogenated polyols thereof, polyolsobtained by copolymerizing a polybutadiene-based polyol with an olefiniccompound such as styrene, ethylene, vinyl acetate, or an acrylate esterand hydrogenated polyols thereof, and the like. In particular,polybutadiene polyol, polyisoprene polyol, hydrogenated polybutadienepolyol, and hydrogenated polyisoprene polyol are preferred. These may beused solely or as a combination of two or more kinds thereof.

The content of the olefinic polyol as the (B) component is preferably40% by mass or more and 90% by mass or less with respect to thepolyurethane in the polyurethane water dispersion. When the contentfalls within the range, the bindability and the resistance to anelectrolytic solution are particularly excellent.

As the (B) component in the present invention, other than the olefinicpolyol, there can be also used a polycarbonate diol having a carbonnumber between carbonate bond chains of less than 6. When the carbonnumber between carbonate bond chains is less than 6, the affinity to theelectrolytic solution becomes satisfactory and ion conductivity isimproved.

The polycarbonate diol can be obtained by transesterification of acarbonate ester with a diol and removal of the formed alcohol by meansof distillation or the like.

As the diol, there may be mentioned linear, cyclic or branched aliphaticdiols having a carbon number of 2 to 5. More specifically, there may bementioned 1,3-butanediol, 1,3-propanediol, 1,4-butanediol,2,3-butanediol, ethylene glycol, diethylene glycol, propylene glycol,dipropylene glycol, 1,5-pentanediol, neopentyl glycol (hereinafterabbreviated as NPG), 2-methyl-1,3-propanediol,2,2-methyl-1,3-propanediol, 2-ethyl-1,3-propanediol,2,2-diethyl-1,3-propanediol, and the like. The diols may be used solelyor as a combination of two or more kinds thereof.

Examples of the carbonate ester include alkylene carbonates, dialkylcarbonates and diaryl carbonates. As the alkylene carbonates, there maybe mentioned ethylene carbonate, trimethylene carbonate, 1,2-propylenecarbonate, 1,2-butylene carbonate, 1,3-butylene carbonate, 1,2-pentylenecarbonate, and the like. Moreover, as the dialkyl carbonates, there maybe mentioned dimethyl carbonate, diethyl carbonate, di-n-butylcarbonate, and the like. As the diaryl carbonates, there may bementioned diphenyl carbonate and the like. Among them, the use ofethylene carbonate, dimethyl carbonate, diethyl carbonate, or di-n-butylcarbonate is preferred.

The catalyst to be used in the transesterification reaction of thecarbonate ester with the aliphatic diol is not particularly limited but,as a suitable catalyst, there may be mentioned a hydroxide of an alkalimetal or an alkaline earth metal, such as sodium hydroxide or potassiumhydroxide, a metal alcoholate such as sodium methylate, potassiummethylate, titanium tetraisopropylate, or zirconium tetraisopropylate, atitanium compound such as tetraisopropoxytitanium ortetra-n-butoxytitanium, a metal salt of acetic acid, such as magnesiumacetate, calcium acetate, zinc acetate, or lead acetate, and the like.

The above-obtained polycarbonate diols of the above (B) may be usedsolely or as a combination of two or more kinds thereof.

The content of the polycarbonate diol as the (B) component is preferably50% by mass or more and 90% by mass or less with respect to thepolyurethane in the polyurethane water dispersion. When the content is50% by mass or more, the bindability is particularly excellent, and whenit is 90% by mass or less, the resistance to an electrolytic solution isparticularly excellent.

The molecular weight of the (B) component is preferably 500 or more and5,000 or less in terms of number-average molecular weight. When thenumber-average molecular weight falls within the range, the bindabilityis particularly excellent, and in the case where the (B) component is anolefinic polyol, the resistance to an electrolytic solution is alsoparticularly excellent.

As the (B) compound having two or more active hydrogen groups, inaddition to the above-described ones, for example, a polyether, apolyester, a polyether ester, a polycarbonate, a polythioether, apolyacetal, an acrylic, a polysiloxane, a fluorine-based, or a vegetableoil-based compound or the like may be used in combination. Morespecifically, there may be mentioned polyhydric alcohols such asethylene glycol, propylene glycol, propanediol, butanediol, pentanediol,3-methyl-1,5-pentanediol, hexanediol, neopentyl glycol, diethyleneglycol, triethylene glycol, tetraethylene glycol, polyethylene glycol,dipropylene glycol, tripropylene glycol, 1,4-cyclohexanedimethanol,bisphenol A, bisphenol F, bisphenol S, hydrogenated bisphenol A,dibromobisphenol A, dihydroxyethyl terephthalate, hydroquinonedihydroxyethyl ether, trimethylolpropane, glycerin, and pentaerythritol,oxyalkylene derivatives thereof, ester compounds of the polyhydricalcohols or the oxyalkylene derivatives thereof with polybasiccarboxylic acids, polybasic carboxylic acid anhydrides or polybasiccarboxylic acid esters, and polyol compounds such as a polycarbonatepolyol, a polycaprolactone polyol, a polyester polyol, a polthioetherpolyol, a polyacetal polyol, a polytetramethylene glycol, a fluorinepolyol, a silicon polyol, an acryl polyol, a dimer acid-based polyol, acastor oil-based polyol, and a soybean oil-based polyol, and modifiedproducts thereof. As the alkylene oxide, there may be mentioned ethyleneoxide, propylene oxide, butylene oxide, and the like. The compoundshaving two or more active hydrogen groups may be used solely or as acombination of two or more kinds thereof. Among them, the combined usedof a polycarbonate polyol, a castor oil-based polyol, or a dimeracid-based polyol is preferred. The number-average molecular weight ofthe compound to be used in combination is preferably 500 or more and5,000 or less.

The (C) component to be used in the present invention is a compoundhaving one or more active hydrogen groups and a hydrophilic group. Asthe hydrophilic group, there may be mentioned an anionic hydrophilicgroup, a cationic hydrophilic group and a nonionic hydrophilic group.Specifically, as the anionic hydrophilic group, there may be mentioned acarboxyl group and a salt thereof, and a sulfonic acid group and a saltthereof, as the cationic hydrophilic group, there may be mentioned atertiary ammonium salt and a quaternary ammonium salt, and as thenonionic hydrophilic group, there may be mentioned a group composed of arepeating unit of ethylene oxide, a group composed of a repeating unitof ethylene oxide and a repeating unit of another alkylene oxide, andthe like.

Examples of the compound having one or more active hydrogen groups and acarboxyl group include carboxylic acid-containing compounds such as2,2-dimethylolpropionic acid, 2,2-dimethylolbutyric acid,2,2-dimethylolvaleric acid, dioxymaleic acid, 2,6-dioxybenzoic acid, and3,4-diaminobenzoic acid, derivatives thereof, and salts thereof, andalso include polyester polyols obtained by using them. Furthermore,there may be mentioned amino acids such as alanine, aminobutyric acid,aminocaproic acid, glycine, glutamic acid, aspartic acid, and histidine,and carboxylic acids such as succinic acid, adipic acid, maleicanhydride, phthalic acid, and trimellitic anhydride.

Examples of the compound having one or more active hydrogen groups and asulfonic acid group or a salt thereof include sulfonic acid-containingcompounds such as 2-oxyethanesulfonic acid, phenolsulfonic acid,sulfobenzoic acid, sulfosuccinic acid, 5-sulfoisophthalic acid,sulfanilic acid, 1,3-phenylenediamine-4,6-disulfonic acid and2,4-diaminotoluene-5-sulfonic acid and derivatives thereof, andpolyester polyols, polyamide polyols and polyamide polyester polyols,which are obtained through copolymerization of those compounds.

The polyurethane finally obtained can be made water-dispersible byneutralizing the carboxyl group or the sulfonic acid group to form asalt. Examples of the neutralizing agent in this case includenonvolatile bases such as sodium hydroxide and potassium hydroxide, andvolatile bases such as tertiary amines such as trimethylamine,triethylamine, dimethylethanolamine, methyldiethanolamine, andtriethanolamine, and ammonia. The neutralization may be performed eitherbefore the urethanization reaction, during the reaction, or after thereaction.

As the compound having one or more active hydrogen groups and a tertiaryammonium salt, there may be mentioned alkanolamines such asmethylaminoethanol and methyldiethanolamine. The polyurethane can bemade water-dispersible by neutralizing those with an organic carboxylicacid such as formic acid or acetic acid or an inorganic acid such ashydrochloric acid or sulfuric acid to form a salt. The neutralizationmay be performed either before the urethanization reaction, during thereaction, or after the reaction. Among them, a compound obtained throughneutralization of methyldiethanolamine with an organic carboxylic acidis preferred from the standpoint of the easiness of emulsification ofthe polyurethane.

The compound having one or more active hydrogen groups and a quaternaryammonium salt is a compound obtained through quatemarization of theaforementioned alkanolamine such as methylaminoethanol ormethyldiethanolamine with an alkyl halide such as methyl chloride ormethyl bromide, or with a dialkyl sulfate such as dimethyl sulfate.Among them, a compound obtained through quaternarization ofmethyldiethanolamine with dimethyl sulfate is preferred from thestandpoint of the easiness of emulsification of the polyurethane.

The compound having one or more active hydrogen groups and a nonionichydrophilic group is not particularly limited, and a compound thatcontains at least 30% by mass or more of a repeating unit of ethyleneoxide and has a number-average molecular weight of 300 to 20,000 ispreferred. Examples thereof include nonionic group-containing compoundssuch as a polyoxyethylene glycol, a polyoxyethylene-polyoxypropylenecopolymer glycol, a polyoxyethylene-polyoxybutylene copolymer glycol, apolyoxyethylene-polyoxyalkylene copolymer glycol, and monoalkyl ethersthereof, and polyester polyether polyols obtained throughcopolymerization thereof.

As the (C) component, the above-described compounds may be used solelyor as a combination of two or more kinds thereof.

With regard to the content of the (C) component, in the case of theanionic hydrophilic group-containing compound, an acid value indicatingthe content of the anionic hydrophilic group is preferably from 5 to 50mgKOH/g and more preferably from 5 to 45 mgKOH/g. When the acid value is5 mgKOH/g or more, the dispersibility in water is particularlysatisfactory. When the acid value is 50 mgKOH/g or less, the resistanceto an electrolytic solution is particularly excellent. The acid valuecan be determined from the amount of KOH (mg) that is required forneutralizing the free carboxyl group contained in 1 g of solid contentof the polyurethane water dispersion in accordance with JIS K0070-1992.In the case where the nonionic group-containing compound is used, theamount thereof used is preferably from 1 to 30% by mass, andparticularly preferably from 5 to 20% by mass. Among them, the (C)component is preferably a compound having one or more active hydrogengroups and a carboxyl group in a molecule from the standpoint of theadhesiveness to a collector.

As the (D) component, use can be made of a chain extending agent that isordinarily used in this field of art. It is not particularly limitedand, specifically, diamines or polyamines can be used. Examples of thediamines include ethylenediamine, trimethylenediamine, piperazine, andisophoronediamine, and examples of the polyamines includediethylenetriamine, dipropylenetriamine and triethylenetetramine.

The number-average molecular weight of the polyurethane to be containedin the binder of the present invention is preferably made as large aspossible by introducing a branched structure or an internal crosslinkedstructure, and is preferably 50,000 or more. When the molecular weightis increased to make the polyurethane insoluble in a solvent, it becomeseasy to obtain a coated film that is excellent in the resistance to anelectrolytic solution.

The production method of the polyurethane water dispersion of thepresent invention is not particularly limited but, for example, thefollowing method is used. The (A) polyisocyanate in an amount that isstoichiometrically excessive to the total amount of the active hydrogengroups that are contained in the (B) compound having two or more activehydrogen groups, the (C) compound having one or more active hydrogengroups and a hydrophilic groups and the (D) chain extending agent andthat have reactivity with the isocyanate group (the equivalent ratio ofthe isocyanate group to the active functional group is 1:0.85 to 1.1) issubjected to a reaction without a solvent or in an organic solventhaving no active hydrogen group to synthesize a urethane prepolymerhaving an isocyanate terminal. Then, neutralization or quaternarizationof the anionic hydrophilic group or the cationic hydrophilic group ofthe (C) component is performed depending on necessity, followed bydispersion and emulsification in water. Thereafter, the (D) chainextending agent in a smaller equivalent amount to the residualisocyanate group (the equivalent ratio of the isocyanate group to thechain extending agent is 1:0.5 to 0.9) is added thereto, and theisocyanate group in the emulsion micelle and the (D) chain extendingagent are subjected to interfacial polymerization to form a urea bond.According to the procedure, the crosslinking density in the emulsionmicelle is increased, and a three-dimensional crosslinked structure isformed. The formation of the three-dimensional crosslinked structureprovides a coated film exhibiting excellent resistance to anelectrolytic solution. Thereafter, the solvent used is removed dependingon necessity, and thereby the polyurethane water dispersion can beprovided. The chain extension can be also performed with water moleculespresent in the system at the time of dispersing and emulsifying inwater, without the use of the polyamine or the like as the (D)component.

In the synthesis of the urethane prepolymer, such a solvent can be alsoused that is inactive to an isocyanate group and is capable ofdissolving the urethane prepolymer to be formed. As the solvent, theremay be mentioned dioxane, methyl ethyl ketone, dimethylformamide,tetrahydrofuran, N-methyl-2-pyrrolidine, toluene, propylene glycolmonomethyl ether acetate, and the like. These hydrophilic organicsolvents used in the reaction are preferably removed finally.

The average particle diameter of the polyurethane water dispersion to beused in the present invention is preferably in a range of from 0.005 to0.5 μm from the standpoint of the amount to be added, the coatingproperty and the bindability.

The polyurethane to be used in the present invention preferably has acrosslinking density of from 0.01 to 0.50 per 1,000 molecular weight ofthe polyurethane resin. When the crosslinking density is 0.01 or more,the resistance to an electrolytic solution and the heat resistance areparticularly excellent, and when it is 0.50 or less, flexibility of theurethane resin is obtained, and bindability becomes particularlyexcellent.

The crosslinking density referred herein can be obtained by calculationaccording to an expression represented by the following MathematicalExpression 1. Specifically, the crosslinking density per 1,000 molecularweight of polyurethane can be determined by a calculation according tothe following Mathematical Expression 1 , where the polyurethane hasbeen obtained through reaction of W_(A1) g of the polyisocyanate (A)having a molecular weight of MW_(A1) and a functional group number ofF_(A1), W_(A2) g of the polyisocyanate (A) having a molecular weight ofMW_(A2) and a functional group number of F_(A2), W_(Aj) g of thepolyisocyanate (A) having a molecular weight of MW_(Aj) and a functionalgroup number of F_(Aj) (j represents an integer of 1 or more), W_(B1) gof the active hydrogen group-containing compound (B) having a molecularweight of MW_(B1) and a functional group number of F_(B1), W_(B2) g ofthe active hydrogen group-containing compound (B) having a molecularweight of MW_(B2) and a functional group number of F_(B2), W_(Bk) g ofthe active hydrogen group-containing compound (B) having a molecularweight of MW_(Bk) and a functional group number of F_(Bk) (k representsan integer of 1 or more), W_(C1) g of the compound (C) having one ormore active hydrogen groups and a hydrophilic group, which has amolecular weight of MW_(C1) and a functional group number of F_(C1),W_(Cm) g of the compound (C) having one or more active hydrogen groupsand a hydrophilic group, which has a molecular weight of MW_(Cm), and afunctional group number of F_(Cm), (m represents an integer of 1 ormore), W_(D1) g of the chain extending agent (D) having a molecularweight of MW_(D1) and a functional group number of F_(D1), and W_(Dn)ofthe chain extending agent (D) having a molecular weight of MW_(Dn) and afunctional group number of F_(Dn), (n represents an integer of 1 ormore).

$\begin{matrix}{\mspace{79mu}{{{Mathematical}\mspace{14mu}{Expression}\text{:}}{\begin{matrix}{Crosslinking} \\{density}\end{matrix} = {\left\lbrack {\frac{\begin{matrix}{\left\{ {{{W_{A\; 1}\left( {F_{A\; 1} - 2} \right)}/M}\; W_{A\; 1}} \right\} +} \\{\left\{ {{{W_{A\; 2}\left( {F_{A\; 2} - 2} \right)}/M}\; W_{A\; 2}} \right\} +} \\{\ldots + \left\{ {{{W_{A\; j}\left( {F_{A\; j} - 2} \right)}/M}\; W_{A\; j}} \right\}}\end{matrix}}{\begin{matrix}{\left( {W_{A\; 1} + W_{A\; 2} + \ldots + W_{Aj}} \right) +} \\{\left( {W_{B\; 1} + W_{B\; 2} + \ldots + W_{B\; k}} \right) +} \\{\left( {W_{C\; 1} + \ldots + W_{C\; m}} \right) + \left( {W_{D\; 1} + \ldots + W_{D\; n}} \right)}\end{matrix}} + \frac{\begin{matrix}{\left\{ {{{W_{B\; 1}\left( {F_{B\; 1} - 2} \right)}/M}\; W_{B\; 1}} \right\} +} \\{\left\{ {{{W_{B\; 2}\left( {F_{B\; 2} - 2} \right)}/M}\; W_{B\; 2}} \right\} +} \\{\ldots + \left\{ {{{W_{Bk}\left( {F_{Bk} - 2} \right)}/M}\; W_{Bk}} \right\}}\end{matrix}}{\begin{matrix}{\left( {W_{A\; 1} + W_{A\; 2} + \ldots + W_{Aj}} \right) +} \\{\left( {W_{B\; 1} + W_{B\; 2} + \ldots + W_{B\; k}} \right) +} \\{\left( {W_{C\; 1} + \ldots + W_{C\; m}} \right) + \left( {W_{D\; 1} + \ldots + W_{D\; n}} \right)}\end{matrix}} + \frac{\begin{matrix}{\left( {{{W_{C\; 1}\left( {F_{C\; 1} - 2} \right)}/M}\; W_{C\; 1}} \right) +} \\{\ldots + \left( {{{W_{Cm}\left( {F_{Cm} - 2} \right)}/M}\; W_{Cm}} \right)}\end{matrix}}{\begin{matrix}{\left( {W_{A\; 1} + W_{A\; 2} + \ldots + W_{Aj}} \right) +} \\{\left( {W_{B\; 1} + W_{B\; 2} + \ldots + W_{B\; k}} \right) +} \\{\left( {W_{C\; 1} + \ldots + W_{C\; m}} \right) + \left( {W_{D\; 1} + \ldots + W_{D\; n}} \right)}\end{matrix}} + \frac{\begin{matrix}{\left( {{{W_{D\; 1}\left( {F_{D\; 1} - 2} \right)}/M}\; W_{D\; 1}} \right) +} \\{\ldots + \left( {{{W_{Dn}\left( {F_{Dn} - 2} \right)}/M}\; W_{Dn}} \right)}\end{matrix}}{\begin{matrix}{\left( {W_{A\; 1} + W_{A\; 2} + \ldots + W_{Aj}} \right) +} \\{\left( {W_{B\; 1} + W_{B\; 2} + \ldots + W_{B\; k}} \right) +} \\{\left( {W_{C\; 1} + \ldots + W_{C\; m}} \right) + \left( {W_{D\; 1} + \ldots + W_{D\; n}} \right)}\end{matrix}}} \right\rbrack \times 1000}}}} & \left\lbrack {{Math}.\mspace{14mu} 1} \right\rbrack\end{matrix}$

In the case where the (B) compound having two or more active hydrogengroups contains an olefinic polyol, the urea bond equivalent of thepolyurethane is preferably from 400 to 10,000 g/eq. When the urea bondequivalent is 400 g/eq or more, the polyurethane is particularlyexcellent in the flexibility and the bindability, and when it is 10,000g/eq or less, the workability during synthesis is satisfactory and theresistance to an electrolytic solution and the heat resistance are alsoparticularly excellent.

On the other hand, in the case where the (B) compound having two or moreactive hydrogen groups contains a polycarbonate diol having a carbonnumber between carbonate bond chains of less than 6, the urea bondequivalent of the polyurethane is preferably from 300 to 20,000 g/eq,and more preferably from 400 to 10,000 g/eq. When the urea bondequivalent is 300 g/eq or more, the polyurethane is particularlyexcellent in the flexibility and the bindability, and when it is 20,000g/eq or less, the workability during synthesis is satisfactory and theresistance to an electrolytic solution and the heat resistance are alsoexcellent.

Here, the urea bond equivalent of the polyurethane is number-averagemolecular weight per urea bond in one molecule of the polyurethane andcan be determined by calculation according to an expression representedby the following Mathematical Expression 2. The letters in theexpression mean the same as the letters in the Mathematical Expression1.

$\begin{matrix}{\mspace{79mu}{{{Mathematical}\mspace{14mu}{Expression}\mspace{14mu} 2\text{:}}{{{Urea}\mspace{14mu}{bond}\mspace{14mu}{equivalent}} = \frac{(1)}{\frac{\left\{ \begin{matrix}\left( {{W_{A\; 1} \times {F_{A\; 1}/M}\; W_{A\; 1}} + {W_{A\; 2} \times {F_{A\; 2}/M}\; W_{A\; 2}} + \ldots +} \right. \\\begin{matrix}{\left. {W_{Aj} \times {F_{Aj}/M}\; W_{Aj}} \right) - \left( {{W_{B\; 1} \times {F_{B\; 1}/M}\; W_{B\; 1}} + {W_{B\; 2} \times}} \right.} \\{\left. {{{F_{B\; 2}/M}\; W_{B\; 2}} + \ldots + {W_{Bk} \times {F_{Bk}/M}\; W_{Bk}}} \right) -}\end{matrix} \\\left( {{W_{C\; 1} \times {F_{C\; 1}/M}\; W_{C\; 1}} + \ldots + {W_{Cm} \times {F_{Cm}/M}\; W_{Cm}}} \right)\end{matrix} \right\}}{\begin{Bmatrix}{\left( {W_{A\; 1} + W_{A\; 2} + \ldots + W_{Aj}} \right) + \left( {W_{B\; 1} + W_{B\; 2} + \ldots + W_{Bk}} \right) +} \\{\left( {W_{C\; 1} + \ldots + W_{Cm}} \right) + \left( {W_{D\; 1} + \ldots + W_{Dn}} \right)}\end{Bmatrix}}}}}} & \left\lbrack {{Math}.\mspace{14mu} 2} \right\rbrack\end{matrix}$

In the case where the (B) compound having two or more active hydrogengroups contains an olefinic polyol, the polyurethane of the presentinvention has a urethane bond equivalent of preferably from 300 to 1,500g/eq. When the urethane bond equivalent is 300 g/eq or more, thepolyurethane has sufficient flexibility and is particularly excellent inthe resistance to an electrolytic solution and the bonding capability,and when it is 1,500 g/eq or less, it is particularly excellent in thebonding capability.

In the case where the (B) compound having two or more active hydrogengroups contains a polycarbonate diol having a carbon number betweencarbonate bond chains of less than 6, the polyurethane of the presentinvention has a urethane bond equivalent of preferably from 200 to 2,000g/eq, and more preferably from 300 to 1,000 g/eq. When the urethane bondequivalent falls within the range, the bonding capability and theresistance to an electrolytic solution are particularly excellent.

Here, the urethane bond equivalent of the polyurethane is number-averagemolecular weight per urethane bond in one molecule of the polyurethaneand can be determined by calculation according to an expressionrepresented by the following Mathematical Expression 3. The letters inthe expression mean the same as the letters in the MathematicalExpression 1.

$\begin{matrix}{\mspace{79mu}{{{Mathematical}\mspace{14mu}{Expression}\mspace{14mu} 3\text{:}}{{{Urethane}\mspace{14mu}{bond}\mspace{14mu}{equivalent}} = \frac{1}{\frac{\begin{matrix}\left( {{W_{A\; 1} \times {F_{A\; 1}/M}\; W_{A\; 1}} + {W_{A\; 2} \times {F_{A\; 2}/M}\; W_{A\; 2}} +} \right. \\\left. {\ldots + {W_{Aj} \times {F_{Aj}/M}\; W_{Aj}}} \right)\end{matrix}}{\begin{Bmatrix}{\left( {W_{A\; 1} + W_{A\; 2} + \ldots + W_{Aj}} \right) + \left( {W_{B\; 1} +} \right.} \\\begin{matrix}{\left. {W_{B\; 2} + \ldots + W_{Bk}} \right) + \left( {W_{C\; 1} + \ldots +} \right.} \\{\left. W_{Cm} \right) + \left( {W_{D\; 1} + \ldots + W_{Dn}} \right)}\end{matrix}\end{Bmatrix}} - \frac{1}{\begin{matrix}{{Urea}\mspace{14mu}{bond}} \\{equivalent}\end{matrix}}}}}} & \left\lbrack {{Math}.\mspace{14mu} 3} \right\rbrack\end{matrix}$

In the case where the (B) component contains a polycarbonate diol, thecarbonate bond equivalent of the polyurethane of the present inventionis preferably 500 g/eq or less. When it is 500 g/eq or less, theaffinity to an electrolytic solution is satisfactory and the charge anddischarge characteristics are particularly excellent.

Here, the carbonate bond equivalent of the polyurethane isnumber-average molecular weight per carbonate bond in one molecule ofthe polyurethane. Specifically, the carbonate bond equivalent ofpolyurethane can be determined by calculation according to the followingMathematical Expression 4, in the case where the polyurethane has beenobtained through reaction of W_(A1) g of the polyisocyanate (A) having amolecular weight of MW_(A1) and a functional group number of F_(A1),W_(A2) g of the polyisocyanate (A) having a molecular weight of MW_(A2)and a functional group number of F_(A2), W_(Aj) g of the polyisocyanate(A) having a molecular weight of MW_(Aj) and a functional group numberof F_(Aj) (j represents an integer of 1 or more), W_(B1) g of the activehydrogen group-containing compound (B) having a molecular weight ofMW_(B1) and a functional group number of F_(B1), W_(B2) g of the activehydrogen group-containing compound (B) having a molecular weight ofMW_(B2) and a functional group number of F_(B2), W_(Bk) g of the activehydrogen group-containing compound (B) having a molecular weight ofMW_(Bk) and a functional group number of F_(Bk) (k represents an integerof 1 or more), W_(C1) g of the compound (C) having one or more activehydrogen groups and a hydrophilic group, which has a molecular weight ofMW_(C1) and a functional group number of F_(C1), W_(Cm) g of thecompound (C) having one or more active hydrogen groups and a hydrophilicgroup, which has a molecular weight of MW_(Cm) and a functional groupnumber of F_(Cm), (m represents an integer of 1 or more), W_(D1) g ofthe chain extending agent (D) having a molecular weight of MW_(D1) and afunctional group number of F_(D1), and W_(Dn) g of the chain extendingagent (D) having a molecular weight of MW_(Dn) and a functional groupnumber of F_(Dn) (n represents an integer of 1 or more), in which theactive hydrogen group-containing compound (B) having a molecular weightof MW_(B1) and a functional group number of F_(B1) is a polycarbonatediol (B) having a molecular weight of MW_(B1a).

$\begin{matrix}{\mspace{79mu}{{{Mathematical}\mspace{14mu}{Expression}\mspace{14mu} 4\text{:}}{{{Carbonate}\mspace{14mu}{bond}\mspace{14mu}{equivalent}} = \frac{\left( {{MW}_{B\; 1a} + 26} \right)}{\frac{\left( W_{B\; 1} \right)}{\begin{Bmatrix}{\left( {W_{A\; 1} + W_{A\; 2} + \ldots + W_{Aj}} \right) + \left( {W_{B\; 1} + W_{B\; 2} + \ldots + W_{Bk}} \right) +} \\{\left( {W_{C\; 1} + \ldots + W_{Cm}} \right) + \left( {W_{D\; 1} + \ldots + W_{Dn}} \right)}\end{Bmatrix}}}}}} & \left\lbrack {{Math}.\mspace{14mu} 4} \right\rbrack\end{matrix}$

In the present invention, a crosslinking agent may also be used inproduction of the polyurethane water dispersion. Examples of thecrosslinking agent include aziridine, oxazoline, modifiedpolyisocyanate, and polyepoxide compounds, and these crosslinking agentsmay be used solely or as a combination of two or more kinds thereof.

A positive electrode and a negative electrode to be used in the lithiumsecondary battery each are constituted by an electrode active substance,a conductive agent, a binder for binding the electrode active substanceand the conductive agent to a collector, and the like. The lithiumsecondary battery of the present invention is constituted by using anelectrode that is produced by using a binder containing the polyurethanewater dispersion. The binder may be utilized in both the positiveelectrode and the negative electrode.

In the lithium secondary battery of the present invention, as the binderfor an electrode in which the binder for an electrode, which containsthe polyurethane resin water dispersion of the present invention is notused, use can be made of such polymers as polyvinylidene fluoride, apolyvinylidene fluoride copolymer resin such as a copolymer ofpolyvinylidene fluoride with hexafluoropropylene, perfluoromethyl vinylether or tetrafluoroethylene, a fluorine resin such aspolytetrafluoroethylene and fluorine rubber, styrene-butadiene rubber,ethylene-propylene rubber, and a styrene-acrylonitrile copolymer withoutlimitation thereto.

The positive electrode active substance to be used in the positiveelectrode of the lithium secondary battery of the present invention isnot particularly limited as far as it can perform insertion anddesorption of lithium ions. Examples thereof include metal oxides suchas CuO, Cu₂O, MnO₂, MoO₃, V₂O₅, CrO₃, Fe₂O₃, Ni₂O₃, and CoO₃, compositeoxides of lithium and a transition metal, such as Li_(x)CoO₂,Li_(x)NiO₂, Li_(x)Mn₂O₄, and LiFePO₄, metal chalcogen compounds such asTiS₂, MoS₂ and NbSe₃, and conductive polymer compounds such aspolyacene, poly-para-phenylene, polypyrrole, and polyaniline. Among theabove-described ones, composite oxides of one or more kinds selectedfrom transition metals including cobalt, nickel and manganese withlithium, which are generally referred to as a high voltage system, arepreferred from the standpoints of releasability of lithium ion andeasily obtaining a high voltage. Specific examples of the compositeoxides of cobalt, nickel or manganese with lithium include LiCoO₂,LiMnO₂, LiMn₂O₄, LiNiO₂, LiNi_(x)Co_((1-x))O₂, and LiMn_(a)Ni_(b)Co_(c)(a+b+c=1). It is also possible to use a material obtained by doping thelithium composite oxides with a small amount of an element such asfluorine, boron, aluminum, chromium, zirconium, molybdenum, or iron, orthe lithium composite oxides whose particle surfaces are subjected to asurface treatment with carbon, MgO, Al₂O₃, SiO₂, or the like. Thepositive electrode active substance may be used as a combination of twoor more kinds thereof.

As the negative electrode active substance to be used in the negativeelectrode of the present invention, any known active substance can beused without particular limitation as far as it is capable of performinginsertion and desorption of metal lithium or lithium ions. For example,carbon materials such as natural graphite, artificial graphite, hardlygraphitizable carbon, and easily graphitizable carbon can be used. Also,a metal material such as metal lithium, an alloy and a tin compound, alithium transition metal nitride, a crystalline metal oxide, anamorphous metal oxide, a silicon compound, a conductive polymer, and thelike can be used, and specific examples thereof include Li₄Ti₅O₁₂ andNiSi₅C₆.

A conductive agent is used in the positive electrode and the negativeelectrode of the lithium secondary battery of the present invention. Anyelectronic conductive material that does not adversely affect thebattery performance may be used as the conductive agent withoutparticular limitation. In general, carbon black such as acetylene blackand Ketjen black is used, and such conductive materials may be used asnatural graphite (e.g., squamate graphite, scaly graphite and earthygraphite), artificial graphite, carbon whiskers, carbon fibers, metal(e.g., copper, nickel, aluminum, silver, and gold) powders, metalfibers, and conductive ceramic materials. These materials may be used asa mixture of two or more kinds thereof. The amount thereof to be addedis preferably from 0.1 to 30% by mass, and more preferably from 0.2 to20% by mass with respect to the active substance.

As the collector for the electrode active substance of the lithiumsecondary battery of the present invention, any electronic conductivematerial that does not adversely affect the battery constituted may beused without particular limitation. For example, as the collector forthe positive electrode, there can be used aluminum, titanium, stainlesssteel, nickel, sintered carbon, a conductive polymer, conductive glass,and the like, and also aluminum, copper or the like whose surface issubjected to a treatment with carbon, nickel, titanium, silver, or thelike for the purpose of enhancing the adhesion property, theconductivity and the oxidation resistance. As the collector for thenegative electrode, there can be used copper, stainless steel, nickel,aluminum, titanium, sintered carbon, a conductive polymer, conductiveglass, an Al—Cd alloy, and the like, and also copper or the like whosesurface is subjected to a treatment with carbon, nickel, titanium,silver, or the like for the purpose of enhancing the adhesion property,the conductivity and the oxidation resistance. The surface of thematerial for the collector may be subjected to an oxidation treatment.With regard to the shape thereof, there may be used a foil form, andalso a film form, a sheet form, a net form, a punched or expandedmember, and a molded body such as a lath body, a porous body and afoamed body. The thickness thereof is not particularly limited, and onehaving a thickness of from 1 to 100 μm may be generally used.

The electrode of the lithium secondary battery of the present inventionmay be produced by mixing the electrode active substance, a conductiveagent, a collector for the electrode active substance, a binder forbinding the electrode active substance and the conductive agent to thecollector, and the like to prepare an electrode material in a slurryform, applying the material on an aluminum foil, a copper foil or thelike as a collector, and evaporating the dispersion medium.

In the electrode material of the present invention, a thickener such asa water soluble polymer can be used as a viscosity controlling agent forforming the slurry. Specifically, use can be made of one kind or two ormore kinds selected from cellulose compounds such as a carboxymethylcellulose salt, methyl cellulose, ethyl cellulose, hydroxymethylcellulose, hydroxypropyl methyl cellulose, and hydroxyethyl methylcellulose; polycarboxylic acid-based compounds such as polyacrylic acidand sodium polyacrylate; compounds having a vinylpyrrolidone structure,such as polyvinylpyrrolidone; polyacrylamide, polyethylene oxide,polyvinyl alcohol, sodium alginate, xanthan gum, carrageenan, guar gum,agar, starch, and the like, and among these, a carboxymethyl cellulosesalt is preferred.

The method, the order and the like of mixing the electrode material arenot particularly limited. For example, the active substance and theconductive agent may be mixed in advance to be used, and for mixing inthis case, a mortar, a mill mixer, a ball mill such as a planetary ballmill or a shaker ball mill, a mechano-fusion, and the like may be used.

As the separator to be used in the lithium secondary battery of thepresent invention, a separator that is used in an ordinary lithiumsecondary battery can be used without particular limitation, andexamples thereof include porous resins formed of a polyethylene, apolypropylene, a polyolefin, a polytetrafluoroethylene, or the like,ceramics, and nonwoven fabrics.

As the electrolytic solution to be used in the lithium secondary batteryof the present invention, an organic electrolytic solution, an ionicliquid, or the like, which is used conventionally in a lithium secondarybattery, may be used without particular limitation.

The electrolyte salt to be used in the lithium secondary battery of thepresent invention is not particularly limited, and examples thereofinclude LiPF₆, LiBF₄, LiClO₄, LiAsF₆, LiCl, LiBr, LiCF₃SO₃,LiN(CF₃SO₂)₂, LiC(CF₃SO₂)₃, LiI, LiAlCl₄, NaClO₄, NaBF₄, and Nal, andparticularly include inorganic lithium salts such as LiPF₆, LiBF₄,LiClO₄, and LiAsF₆ and an organic lithium salt represented byLiN(SO₂C_(x)F_(2x+1))(SO₂C_(y)F_(2y+1)). Here, x and y each represent 0or an integer of from 1 to 4 and x+y is an integer of from 2 to 8.Specifically, as the organic lithium salt, there may be mentionedLiN(SO₂F)₂, LiN(SO₂CF₃)(SO₂C₂F₅), LiN(SO₂CF₃)(SO₂C₃F₇),LiN(SO₂CF₃)(SO₂C₄F₉), LiN(SO₂C₂F₅)₂, LiN(SO₂C₂F₅)(SO₂C₃F₇),LiN(SO₂C₂F₅)(SO₂C₄F₉), and the like. Among these, the use of LiPF₆,LiBF₄, LiN(CF₃SO₂)₂, LiN(SO₂F)₂, LiN(SO₂C₂F₅)₂, or the like for theelectrolyte is preferred due to excellent electric characteristics. Theelectrolyte salts may be used solely or as a combination of two or morekinds thereof. The lithium salt is generally contained in theelectrolytic solution in a concentration of from 0.1 to 2.0 mol/L andpreferably from 0.3 to 1.5 mol/L.

The organic solvent for dissolving the electrolyte salt of the lithiumsecondary battery of the present invention is not particularly limitedas far as it is an organic solvent that is used for a non-aqueouselectrolytic solution in an ordinary lithium secondary battery, andexamples thereof include carbonate compounds, lactone compounds, ethercompounds, sulfolane compounds, dioxolane compounds, ketone compounds,nitrile compounds, and halogenated hydrocarbon compounds. Specifically,there may be mentioned carbonates such as dimethyl carbonate, methylethyl carbonate, diethyl carbonate, ethylene carbonate, propylenecarbonate, ethylene glycol dimethyl carbonate, propylene glycol dimethylcarbonate, ethylene glycol diethyl carbonate, and vinylene carbonate;lactones such as γ-butyrolactone; ethers such as dimethoxyethane,tetrahydrofuran, 2-methyltetrahydrofuran, tetrahydropyran, and1,4-dioxane; sulfolanes such as sulfolane and 3-methylsulfolane;dioxolanes such as 1,3-dioxolane; ketones such as 4-methyl-2-pentanone;nitriles such as acetonitrile, propionitrile, valeronitrile, andbenzonitrile; halogenated hydrocarbons such as 1,2-dichloroethane; ionicliquids of other compounds such as methyl formate, dimethylformamide,diethylformamide, dimethylsulfoxide, an imidazolium salt, and aquaternary ammonium salt; and the like. A mixture of these may be used.

Among the organic solvents, one kind or more of a non-aqueous solventselected from the group consisting of the carbonates is preferablycontained in view of excellent solubility of the electrolyte, dielectricconstant and viscosity.

In the case where a polymer electrolyte or a polymer gel electrolyte isused in the lithium secondary battery of the present invention, theremay be used a polymer compound such as a polymer of an ether, an ester,a siloxane, acrylonitrile, vinylidene fluoride, hexafluoropropylene, anacrylate, a methacrylate, styrene, vinyl acetate, vinyl chloride,oxetane, or the like, a polymer having a copolymer structure thereof, ora crosslinked material thereof. They may be used solely or as acombination of two or more kinds thereof. Without particular limitation,a polymer having an ether structure, such as polyethylene oxide, isparticularly preferred.

In the lithium secondary battery of the present invention, a liquid-typebattery contains an electrolytic solution, a gel-type battery contains aprecursor solution containing a polymer dissolved in an electrolyticsolution, and a solid electrolyte battery contains a pre-crosslinkedpolymer having an electrolyte salt dissolved therein, each in a batterycontainer.

The lithium secondary battery according to the present invention may beformed to a cylindrical shape, a coin shape, a rectangular shape, or anyother arbitrary shape. The basic structure of the battery is the sameregardless of the shape, and the design may be changed to be useddepending on the purpose. In the case of a cylindrical battery, forexample, it can be obtained as follows: a negative electrode composed ofa negative electrode collector coated with a negative electrode activesubstance and a positive electrode composed of a positive electrodecollector coated with a positive electrode active substance are woundwith a separator intervening therebetween to form a wound assembly,which is then housed in a battery canister, and a non-aqueouselectrolytic solution is charged therein, followed by sealing withinsulating plates placed on the top and bottom. In the case ofapplication to a coin lithium secondary battery, a disk-shaped negativeelectrode, a separator, a disk-shaped positive electrode, and stainlesssteel plates are laminated and housed in a coin battery canister, and anon-aqueous electrolytic solution is charged therein, followed bysealing.

EXAMPLES

Examples will be described along with Comparative Examples below, butthe present invention should not be construed as being limited to theseExamples.

[Synthesis of Polyurethane Water Dispersion]

Synthetic Example 1-1 Synthesis of Polyurethane Water Dispersion 1A

To a four-neck flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen blowing tube were added 184.1 parts by massof a polybutadiene polyol (manufactured by Idemitsu Kosan Co., Ltd.,PolybdR-15HT, average hydroxyl value: 102.7 mgKOH/g, number of activehydrogen group: 2.30), 15.4 parts by mass of dimethylolpropionic acid(number of active hydrogen group: 2), 100.5 parts by mass ofdicyclohexylmethane diisocyanate, and 200 parts by mass of methyl ethylketone, and the reaction was carried out at 75° C. for 4 hours to afforda methyl ethyl ketone solution of a urethane prepolymer having a freeisocyanate group content of 2.7% with respect to the nonvolatilecontent. The solution was cooled to 45° C. and neutralized by adding11.6 parts by mass of triethylamine, and then emulsified and dispersedby using a homogenizer while gradually adding 900 parts by mass of waterthereto. Subsequently, an aqueous solution obtained by diluting 5.1parts by mass of ethylenediamine (number of active hydrogen group: 2)with 100 parts by mass of water was added thereto, and chain extendingreaction was performed for 1 hour. The solvent was removed while heatingat 50° C. under reduced pressure, thereby affording a polyurethane waterdispersion 1A having a nonvolatile content of about 30%.

Synthetic Example 1-2 Synthesis of Polyurethane Water Dispersion 1B

To a four-neck flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen blowing tube were added 195.0 parts by massof a polybutadiene polyol (manufactured by Idemitsu Kosan Co., Ltd.,PolybdR-15HT, average hydroxyl value: 102.7 mgKOH/g, number of activehydrogen group: 2.30), 12.6 parts by mass of dimethylolpropionic acid(number of active hydrogen group: 2), 92.4 parts by mass ofdicyclohexylmethane diisocyanate, and 200 parts by mass of methyl ethylketone, and the reaction was carried out at 75° C. for 4 hours to afforda methyl ethyl ketone solution of a urethane prepolymer having a freeisocyanate group content of 2.1% with respect to the nonvolatilecontent. The solution was cooled to 45° C. and neutralized by adding 9.5parts by mass of triethylamine, and then emulsified and dispersed byusing a homogenizer while gradually adding 900 parts by mass of waterthereto. Subsequently, an aqueous solution obtained by diluting 4.6parts by mass of diethylenetriamine (number of active hydrogen group: 3)with 100 parts by mass of water was added thereto, and chain extendingreaction was performed for 1 hour. The solvent was removed while heatingat 50° C. under reduced pressure, thereby affording a polyurethane waterdispersion 1B having a nonvolatile content of about 30%.

Synthetic Example 1-3 Synthesis of Polyurethane Water Dispersion 1C

To a four-neck flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen blowing tube were added 215.3 parts by massof a polybutadiene polyol (manufactured by Idemitsu Kosan Co., Ltd.,PolybdR-45HT, average hydroxyl value: 46.5 mgKOH/g, number of activehydrogen group: 2.32), 15.4 parts by mass of dimethylolpropionic acid(number of active hydrogen group: 2), 69.3 parts by mass ofdicyclohexylmethane diisocyanate, and 200 parts by mass of methyl ethylketone, and the reaction was carried out at 75° C. for 4 hours to afforda methyl ethyl ketone solution of a urethane prepolymer having a freeisocyanate group content of 1.5% with respect to the nonvolatilecontent. The solution was cooled to 45° C. and neutralized by adding11.6 parts by mass of triethylamine, and then emulsified and dispersedby using a homogenizer while gradually adding 900 parts by mass of waterthereto. Subsequently, an aqueous solution obtained by diluting 3.0parts by mass of ethylenediamine (number of active hydrogen group: 2)with 100 parts by mass of water was added thereto, and chain extendingreaction was performed for 1 hour. The solvent was removed while heatingat 50° C. under reduced pressure, thereby affording a polyurethane waterdispersion 1C having a nonvolatile content of about 30%.

Synthetic Example 1-4 Synthesis of Polyurethane Water Dispersion 1D

To a four-neck flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen blowing tube were added 213.6 parts by massof a hydrogenated polyisoprene polyol (manufactured by Idemitsu KosanCo., Ltd., Epol, average hydroxyl value: 50.5 mgKOH/g, number of activehydrogen group: 2.25), 15.4 parts by mass of dimethylolpropionic acid(number of active hydrogen group: 2), 71.0 parts by mass ofdicyclohexylmethane diisocyanate, and 200 parts by mass of methyl ethylketone, and the reaction was carried out at 75° C. for 4 hours to afforda methyl ethyl ketone solution of a urethane prepolymer having a freeisocyanate group content of 1.5% with respect to the nonvolatilecontent. The solution was cooled to 45° C. and neutralized by adding11.6 parts by mass of triethylamine, and then emulsified and dispersedby using a homogenizer while gradually adding 900 parts by mass of waterthereto. Subsequently, an aqueous solution obtained by diluting 2.9parts by mass of ethylenediamine (number of active hydrogen group: 2)with 100 parts by mass of water was added thereto, and chain extendingreaction was performed for 1 hour. The solvent was removed while heatingat 50° C. under reduced pressure, thereby affording a polyurethane waterdispersion 1D having a nonvolatile content of about 30%.

Synthetic Example 1-5 Synthesis of Polyurethane Water Dispersion 1E

To a four-neck flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen blowing tube were added 202.1 parts by massof a polybutadiene polyol (manufactured by Idemitsu Kosan Co., Ltd.,PolybdR-15HT, average hydroxyl value: 102.7 mgKOH/g, number of activehydrogen group: 2.30), 12.6 parts by mass of dimethylolpropionic acid(number of active hydrogen group: 2), 64.56 parts by mass ofdicyclohexylmethane diisocyanate, 20.73 parts by mass of hexamethylenediisocyanate, and 200 parts by mass of methyl ethyl ketone, and thereaction was carried out at 75° C. for 4 hours to afford a methyl ethylketone solution of a urethane prepolymer having a free isocyanate groupcontent of 2.4% with respect to the nonvolatile content. The solutionwas cooled to 45° C. and neutralized by adding 9.5 parts by mass oftriethylamine, and then emulsified and dispersed by using a homogenizerwhile gradually adding 900 parts by mass of water thereto. Subsequently,an aqueous solution obtained by diluting 4.5 parts by mass ofethylenediamine (number of active hydrogen group: 2) with 100 parts bymass of water was added thereto, and chain extending reaction wasperformed for 1 hour. The solvent was removed while heating at 50° C.under reduced pressure, thereby affording a polyurethane waterdispersion 1E having a nonvolatile content of about 30%.

Synthetic Example 1-6 Synthesis of Polyurethane Water Dispersion 1F

To a four-neck flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen blowing tube were added 206.2 parts by massof a polybutadiene polyol (manufactured by Idemitsu Kosan Co., Ltd.,PolybdR-15HT, average hydroxyl value: 102.7 mgKOH/g, number of activehydrogen group: 2.30), 12.6 parts by mass of dimethylolpropionic acid(number of active hydrogen group: 2), 49.5 parts by mass ofdicyclohexylmethane diisocyanate, 31.74 parts by mass of hexamethylenediisocyanate, and 200 parts by mass of methyl ethyl ketone, and thereaction was carried out at 75° C. for 4 hours to afford a methyl ethylketone solution of a urethane prepolymer having a free isocyanate groupcontent of 2.5% with respect to the nonvolatile content. The solutionwas cooled to 45° C. and neutralized by adding 9.5 parts by mass oftriethylamine, and then emulsified and dispersed by using a homogenizerwhile gradually adding 900 parts by mass of water thereto. Subsequently,an aqueous solution obtained by diluting 4.8 parts by mass ofethylenediamine (number of active hydrogen group: 2) with 100 parts bymass of water was added thereto, and chain extending reaction wasperformed for 1 hour. The solvent was removed while heating at 50° C.under reduced pressure, thereby affording a polyurethane waterdispersion 1F having a nonvolatile content of about 30%.

Synthetic Example 1-7 Synthesis of Polyurethane Water Dispersion 1G

To a four-neck flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen blowing tube were added 147.6 parts by massof a polybutadiene polyol (manufactured by Idemitsu Kosan Co., Ltd.,PolybdR-15HT, average hydroxyl value: 102.7 mgKOH/g, number of activehydrogen group: 2.30), 63.27 parts by mass of a polycarbonate polyolcontaining 1,9-nonanediol and methyloctane diol as constituents in amass ratio of 65/35 (manufactured by Kuraray Co., Ltd., Kurapol C-2065N,average hydroxyl value: 58.1 mgKOH/g, number of active hydrogen group:2), 12.6 parts by mass of dimethylolpropionic acid (number of activehydrogen group: 2), 46.62 parts by mass of dicyclohexylmethanediisocyanate, 29.94 parts by mass of hexamethylene diisocyanate, and 200parts by mass of methyl ethyl ketone, and the reaction was carried outat 75° C. for 4 hours to afford a methyl ethyl ketone solution of aurethane prepolymer having a free isocyanate group content of 2.5% withrespect to the nonvolatile content. The solution was cooled to 45° C.and neutralized by adding 9.5 parts by mass of triethylamine, and thenemulsified and dispersed by using a homogenizer while gradually adding900 parts by mass of water thereto. Subsequently, an aqueous solutionobtained by diluting 4.8 parts by mass of ethylenediamine (number ofactive hydrogen group: 2) with 100 parts by mass of water was addedthereto, and chain extending reaction was performed for 1 hour. Thesolvent was removed while heating at 50° C. under reduced pressure,thereby affording a polyurethane water dispersion 1G having anonvolatile content of about 30%.

Synthetic Example 1-8 Synthesis of Polyurethane Water Dispersion 1H

To a four-neck flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen blowing tube were added 220.4 parts by massof a polybutadiene polyol (manufactured by Idemitsu Kosan Co., Ltd.,PolybdR-45HT, average hydroxyl value: 46.5 mgKOH/g, number of activehydrogen group: 2.32), 12.6 parts by mass of dimethylolpropionic acid(number of active hydrogen group: 2), 67.0 parts by mass of polymericMDI, and 200 parts by mass of methyl ethyl ketone, and the reaction wascarried out at 75° C. for 4 hours to afford a methyl ethyl ketonesolution of a urethane prepolymer having a free isocyanate group contentof 2.1% with respect to the nonvolatile content. The solution was cooledto 45° C. and neutralized by adding 9.5 parts by mass of triethylamine,and then emulsified and dispersed by using a homogenizer while graduallyadding 900 parts by mass of water thereto. Subsequently, an aqueoussolution obtained by diluting 4.1 parts by mass of ethylenediamine(number of active hydrogen group: 2) with 100 parts by mass of water wasadded thereto, and chain extending reaction was performed for 1 hour.The solvent was removed while heating at 50° C. under reduced pressure,thereby affording a polyurethane water dispersion 1H having anonvolatile content of about 30%.

Synthetic Example 1-9 Synthesis of Polyurethane Water Dispersion 1I

To a four-neck flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen blowing tube were added 216.0 parts by massof a polyisoprene polyol (manufactured by Idemitsu Kosan Co., Ltd.,Polyip, average hydroxyl value: 46.56 mgKOH/g, number of active hydrogengroup: 2.08), 12.6 parts by mass of dimethylolpropionic acid (number ofactive hydrogen group: 2), 71.40 parts by mass of dicyclohexylmethanediisocyanate, and 200 parts by mass of methyl ethyl ketone, and thereaction was carried out at 75° C. for 4 hours to afford a methyl ethylketone solution of a urethane prepolymer having a free isocyanate groupcontent of 2.3% with respect to the nonvolatile content. The solutionwas cooled to 45° C. and neutralized by adding 9.5 parts by mass oftriethylamine, and then emulsified and dispersed by using a homogenizerwhile gradually adding 900 parts by mass of water thereto. Subsequently,an aqueous solution obtained by diluting 4.4 parts by mass ofethylenediamine (number of active hydrogen group: 2) with 100 parts bymass of water was added thereto, and chain extending reaction wasperformed for 1 hour. The solvent was removed while heating at 50° C.under reduced pressure, thereby affording a polyurethane waterdispersion 1I having a nonvolatile content of about 30%.

Synthetic Example 1-10 Synthesis of Polyurethane Water Dispersion 1J

To a four-neck flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen blowing tube were added 172.8 parts by massof a polybutadiene polyol (manufactured by Idemitsu Kosan Co., Ltd.,PolybdR-45HT, average hydroxyl value: 46.5 mgKOH/g, number of activehydrogen group: 2.32), 43.2 parts by mass of a polycarbonate polyolcontaining 1,9-nonanediol and methyloctane diol as constituents in amass ratio of 65/35 (manufactured by Kuraray Co., Ltd., Kurapol C-2065N,average hydroxyl value: 58.1 mgKOH/g, number of active hydrogen group:2), 12.6 parts by mass of dimethylolpropionic acid (number of activehydrogen group: 2), 71.40 parts by mass of dicyclohexylmethanediisocyanate, and 200 parts by mass of methyl ethyl ketone, and thereaction was carried out at 75° C. for 4 hours to afford a methyl ethylketone solution of a urethane prepolymer having a free isocyanate groupcontent of 2.2% with respect to the nonvolatile content. The solutionwas cooled to 45° C. and neutralized by adding 9.5 parts by mass oftriethylamine, and then emulsified and dispersed by using a homogenizerwhile gradually adding 900 parts by mass of water thereto. Subsequently,an aqueous solution obtained by diluting 4.1 parts by mass ofethylenediamine (number of active hydrogen group: 2) with 100 parts bymass of water was added thereto, and chain extending reaction wasperformed for 1 hour. The solvent was removed while heating at 50° C.under reduced pressure, thereby affording a polyurethane waterdispersion 1J having a nonvolatile content of about 30%.

Synthetic Example 1-11 Synthesis of Polyurethane Water Dispersion 1K

To a four-neck flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen blowing tube were added 180.0 parts by massof a polybutadiene polyol (manufactured by Idemitsu Kosan Co., Ltd.,PolybdR-15HT, average hydroxyl value: 102.7 mgKOH/g, number of activehydrogen group: 2.30), 13.0 parts by mass of dimethylolpropionic acid(number of active hydrogen group: 2), 107.00 parts by mass ofdicyclohexylmethane diisocyanate, and 200 parts by mass of methyl ethylketone, and the reaction was carried out at 75° C. for 4 hours to afforda methyl ethyl ketone solution of a urethane prepolymer having a freeisocyanate group content of 4.0% with respect to the nonvolatilecontent. The solution was cooled to 45° C. and neutralized by adding 8.8parts by mass of triethylamine, and then emulsified and dispersed byusing a homogenizer while gradually adding 900 parts by mass of waterthereto. Subsequently, an aqueous solution obtained by diluting 8.5parts by mass of diethylenetriamine (number of active hydrogen group: 3)with 100 parts by mass of water was added thereto, and chain extendingreaction was performed for 1 hour. The solvent was removed while heatingat 50° C. under reduced pressure, thereby affording a polyurethane waterdispersion 1K having a nonvolatile content of about 30%.

Synthetic Example 1-12 Synthesis of Polyurethane Water Dispersion 1L

To a four-neck flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen blowing tube were added 222.4 parts by massof a polytetramethylene ether glycol (manufactured by BASF, PolyTHF1000, average hydroxyl value: 110 mgKOH/g, number of active hydrogengroup: 2), 12.6 parts by mass of dimethylolpropionic acid (number ofactive hydrogen group: 2), 65.0 parts by mass of hexamethylenediisocyanate, and 200 parts by mass of methyl ethyl ketone, and thereaction was carried out at 75° C. for 4 hours to afford a methyl ethylketone solution of a urethane prepolymer having a free isocyanate groupcontent of 1.8% with respect to the nonvolatile content. The solutionwas cooled to 45° C. and neutralized by adding 9.5 parts by mass oftriethylamine, and then emulsified and dispersed by using a homogenizerwhile gradually adding 900 parts by mass of water thereto. Subsequently,an aqueous solution obtained by diluting 3.5 parts by mass ofethylenediamine (number of active hydrogen group: 2) with 100 parts bymass of water was added thereto, and chain extending reaction wasperformed for 1 hour. The solvent was removed while heating at 50° C.under reduced pressure, thereby affording a polyurethane waterdispersion 1L having a nonvolatile content of about 30%.

Synthetic Example 1-13 Synthesis of Polyurethane Water Dispersion 1M

To a four-neck flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen blowing tube were added 220.0 parts by massof a polytetramethylene ether glycol (manufactured by BASF, PolyTHF1000, average hydroxyl value: 110 mgKOH/g, number of active hydrogengroup: 2), 0.30 parts by mass of trimethylolpropane (number of activehydrogen group: 3), 12.6 parts by mass of dimethylolpropionic acid(number of active hydrogen group: 2), 67.1 parts by mass ofhexamethylene diisocyanate, and 200 parts by mass of methyl ethylketone, and the reaction was carried out at 75° C. for 4 hours to afforda methyl ethyl ketone solution of a urethane prepolymer having a freeisocyanate group content of 2.1% with respect to the nonvolatilecontent. The solution was cooled to 45° C. and neutralized by adding 9.5parts by mass of triethylamine, and then emulsified and dispersed byusing a homogenizer while gradually adding 900 parts by mass of waterthereto. Subsequently, an aqueous solution obtained by diluting 4.1parts by mass of ethylenediamine (number of active hydrogen group: 2)with 100 parts by mass of water was added thereto, and chain extendingreaction was performed for 1 hour. The solvent was removed while heatingat 50° C. under reduced pressure, thereby affording a polyurethane waterdispersion 1M having a nonvolatile content of about 30%.

Synthetic Example 1-14 Synthesis of Polyurethane Water Dispersion 1N

To a four-neck flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen blowing tube were added 182.8 parts by massof a polytetramethylene ether glycol (manufactured by BASF, PolyTHF1000, average hydroxyl value: 110 mgKOH/g, number of active hydrogengroup: 2), 12.70 parts by mass of trimethylolpropane (number of activehydrogen group: 3), 12.6 parts by mass of dimethylolpropionic acid(number of active hydrogen group: 2), 91.90 parts by mass ofhexamethylene diisocyanate, and 200 parts by mass of methyl ethylketone, and the reaction was carried out at 75° C. for 4 hours to afforda methyl ethyl ketone solution of a urethane prepolymer having a freeisocyanate group content of 3.4% with respect to the nonvolatilecontent. The solution was cooled to 45° C. and neutralized by adding 9.5parts by mass of triethylamine, and then emulsified and dispersed byusing a homogenizer while gradually adding 900 parts by mass of waterthereto. Subsequently, an aqueous solution obtained by diluting 7.6parts by mass of diethylenetriamine (number of active hydrogen group: 3)with 100 parts by mass of water was added thereto, and chain extendingreaction was performed for 1 hour. The solvent was removed while heatingat 50° C. under reduced pressure, thereby affording a polyurethane waterdispersion 1N having a nonvolatile content of about 30%.

Synthetic Example 1-15 Synthesis of Polyurethane Water Dispersion 1O

To a four-neck flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen blowing tube were added 117.0 parts by massof a polybutadiene polyol (manufactured by Idemitsu Kosan Co., Ltd.,PolybdR-15HT, average hydroxyl value: 102.7 mgKOH/g, number of activehydrogen group: 2.30), 40.0 parts by mass of 1,4-butanediol (number ofactive hydrogen group: 2), 15.0 parts by mass of dimethylolpropionicacid (number of active hydrogen group: 2), 128.0 parts by mass ofhexamethylene diisocyanate, and 200 parts by mass of methyl ethylketone, and the reaction was carried out at 75° C. for 4 hours to afforda methyl ethyl ketone solution of a urethane prepolymer having a freeisocyanate group content of 2.6% with respect to the nonvolatilecontent. Then, 1.3 parts by mass of monoethylamine was added to thesolution to carry out the reaction, and then cooled to 45° C. andneutralized by adding 11.3 parts by mass of triethylamine. Thereafter,the solution was emulsified and dispersed by using a homogenizer whilegradually adding 900 parts by mass of water thereto. The solvent wasremoved while heating at 50° C. under reduced pressure, therebyaffording a polyurethane water dispersion 10 having a nonvolatilecontent of about 30%.

[Evaluation of Polyurethane Water Dispersion]

Upon individual measurements for the polyurethane water dispersionsobtained, the following methods were used. The results are shown inTable 1 below.

Weight of the nonvolatile content of the polyurethane water dispersion:Measured in accordance with JIS K 6828.

Crosslinking density in the resin solid content of the polyurethanewater dispersion: Calculated according to the above-describedMathematical Expression 1.

Acid value of the polyurethane resin: Measured in accordance with JIS K0070-1992.

Urea bond equivalent and urethane bond equivalent: Calculated accordingto the above-described Mathematical Expression 2 and MathematicalExpression 3, respectively.

Measurement of average particle diameter of the polyurethane waterdispersion: The average particle diameter was measured with MicrotracUPA-UZ152 (manufactured by Nikkiso Co., Ltd.), and a 50% average valuewas calculated as the average particle diameter.

TABLE 1 Content of Average Urethane olefinic Polyurethane particle bondUrea bond polyol of B water Crosslinking diameter Acid value equivalentequivalent component dispersion density (μm) (mgKOH/g) (g/eq) (g/eq) (wt%) 1A 0.15 0.03 21 529 1607 60 1B 0.30 0.09 17 548 2039 64 1C 0.08 0.2021 720 2798 71 1D 0.07 0.05 21 697 2812 71 1E 0.16 0.10 17 535 1793 661F 0.16 0.03 17 528 1710 68 1G 0.12 0.02 17 571 1708 48 1H 0.08 0.12 17794 2000 72 1I 0.02 0.10 17 802 1842 71 1J 0.07 0.13 17 786 1920 57 1K0.41 0.23 18 578 1089 58 1L 0 0.02 17 470 2381 0 1M 0.007 0.02 17 4702015 0 1N 0.57 0.03 17 362 1259 0 1O 0 0.10 21 225 1600 38[Production of Electrodes]

The binders used for production of electrodes are shown in Table 2below.

TABLE 2 Kind of electrode Kind of binder Negative electrode 1-1Polyurethane water dispersion 1A Negative electrode 1-2 Polyurethanewater dispersion 1B Negative electrode 1-3 Polyurethane water dispersion1C Negative electrode 1-4 Polyurethane water dispersion 1D Negativeelectrode 1-5 Polyurethane water dispersion 1E Negative electrode 1-6Polyurethane water dispersion 1F Negative electrode 1-7 Polyurethanewater dispersion 1G Negative electrode 1-8 Polyurethane water dispersion1H Negative electrode 1-9 Polyurethane water dispersion 1I Negativeelectrode 1-10 Polyurethane water dispersion 1J Negative electrode 1-11Polyurethane water dispersion 1K Negative electrode 1-12 Polyurethanewater dispersion 1L Negative electrode 1-13 Polyurethane waterdispersion 1M Negative electrode 1-14 Polyurethane water dispersion 1NNegative electrode 1-15 Polyurethane water dispersion 1O Negativeelectrode 1-16 SBR Negative electrode 1-17 Polyurethane water dispersion1A Negative electrode 1-18 SBR Negative electrode 1-19 Polyurethanewater dispersion 1I Negative electrode 1-20 SBR Positive electrode 1-1Polyvinylidene fluoride Positive electrode 1-2 Polyurethane waterdispersion 1D Positive electrode 1-3 Polyurethane water dispersion 1LPositive electrode 1-4 Polyvinylidene fluoride Positive electrode 1-5Polyurethane water dispersion 1D Positive electrode 1-6 Polyvinylidenefluoride Positive electrode 1-7 Polyurethane water dispersion 1D[Production of Negative Electrode](Negative Electrode 1-1)

With a planetary mixer, 100 g of natural graphite as a negativeelectrode active substance, 0.5 g of carbon black (manufactured byTimcal, Super-P) as a conductive agent, 100 g of a 2% by mass aqueoussolution of carboxymethyl cellulose sodium salt (manufactured by DKS Co.Ltd., trade name: Cellogen WS-C) as a thickener, and 6.7 g of a 30% bymass solution of the polyurethane water dispersion 1A as a binder weremixed to prepare a negative electrode slurry having a solid content of50%. The negative electrode slurry was applied by coating on anelectrolytic copper foil having a thickness of 10 μm with a coatingmachine, dried at 120° C., and then subjected to a roll pressingtreatment, thereby affording a negative electrode 1-1 having a negativeelectrode active substance in an amount of 7 mg/cm².

(Negative Electrodes 1-2 to 1-16)

Negative electrodes were produced in the same manner as in the negativeelectrode 1-1 except that the polyurethane water dispersion 1A waschanged to the polyurethane water dispersions or a styrene-butadienerubber (SBR) as described in Table 2.

(Negative Electrode 1-17)

With a planetary mixer, 100 g of SiO (average particle diameter: 4.5 μm,specific surface area: 5.5 m²/g) as a negative electrode activesubstance, 5 g of carbon black (manufactured by Timcal, Super-P) as aconductive agent, 100 g of a 2% by mass aqueous solution ofcarboxymethyl cellulose sodium salt (manufactured by DKS Co. Ltd., tradename: Cellogen WS-C) as a thickener, and 6.7 g of a 30% by mass solutionof the polyurethane water dispersion 1A as a binder were mixed toprepare a negative electrode slurry having a solid content of 50%. Thenegative electrode slurry was applied by coating on an electrolyticcopper foil having a thickness of 10 μm with a coating machine, dried at120° C., and then subjected to a roll pressing treatment, therebyaffording a negative electrode 1-17 having a negative electrode activesubstance in an amount of 2.5 mg/cm².

(Negative Electrode 1-18)

A negative electrode 1-18 was produced in the same manner as in thenegative electrode 1-17 except that the polyurethane water dispersion 1Awas changed to SBR.

(Negative Electrode 1-19)

With a planetary mixer, 100 g of Li₄Ti₅O₁₂ as a negative electrodeactive substance, 5 g of carbon black (manufactured by Timcal, Super-P)as a conductive agent, 100 g of a 2% by mass aqueous solution ofcarboxymethyl cellulose sodium salt (manufactured by DKS Co. Ltd., tradename: Cellogen WS-C) as a thickener, and 6.7 g of a 30% by mass solutionof the polyurethane water dispersion 1I as a binder were mixed toprepare a negative electrode slurry having a solid content of 50%. Thenegative electrode slurry was applied by coating on an electrolyticcopper foil having a thickness of 10 μm with a coating machine, dried at120° C., and then subjected to a roll pressing treatment, therebyaffording a negative electrode 1-19 having a negative electrode activesubstance in an amount of 9.7 mg/cm².

(Negative Electrode 1-20)

A negative electrode 1-20 was produced in the same manner as in thenegative electrode 1-19 except that the polyurethane water dispersion 1Iwas changed to SBR.

[Production of Positive Electrode]

(Positive Electrode 1-1)

With a planetary mixer, 100 g of LiNi_(1/3)CO_(1/3)Mn_(1/3)O₂ as apositive electrode active substance, 7.8 g of carbon black (manufacturedby Timcal, Super-P) as a conductive agent, 6 g of polyvinylidenefluoride as a binder, and 61.3 g of N-methyl-2-pyrrolidone as adispersion medium were mixed to prepare a positive electrode slurryhaving a solid content of 65%. The positive electrode slurry was appliedby coating on an aluminum foil having a thickness of 20 μm with acoating machine, dried at 130° C., and then subjected to a roll pressingtreatment, thereby affording a positive electrode 1-1 having a positiveelectrode active substance in an amount of 13.8 mg/cm².

(Positive Electrodes 1-2 and 1-3)

With a planetary mixer, 100 g of LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂ as apositive electrode active substance, 7.8 g of carbon black (manufacturedby Timcal, Super-P) as a conductive agent, 100 g of a 2% by mass aqueoussolution of carboxymethyl cellulose sodium salt (manufactured by DKS Co.Ltd., trade name: Cellogen WS-C) as a thickener, and 6.7 g of a 30% bymass solution of the polyurethane water dispersion shown in Table 2 as abinder were mixed to prepare a positive electrode slurry having a solidcontent of 50%. The positive electrode slurry was applied by coating onan aluminum foil having a thickness of 20 μm with a coating machine,dried at 130° C., and then subjected to a roll pressing treatment,thereby affording positive electrodes 1-2 and 1-3 each having a positiveelectrode active substance in an amount of 13.8 mg/cm².

(Positive Electrode 1-4)

With a planetary mixer, 100 g of LiMn₂O₄ as a positive electrode activesubstance, 5 g of carbon black (manufactured by Timcal, Super-P) as aconductive agent, 6 g of polyvinylidene fluoride as a binder, and 59.8 gof N-methyl-2-pyrrolidone as a dispersion medium were mixed to prepare apositive electrode slurry having a solid content of 65%. The positiveelectrode slurry was applied by coating on an aluminum foil having athickness of 20 μm with a coating machine, dried at 130° C., and thensubjected to a roll pressing treatment, thereby affording a positiveelectrode 1-4 having a positive electrode active substance in an amountof 22 mg/cm².

(Positive Electrode 1-5)

With a planetary mixer, 100 g of LiMn₂O₄ as a positive electrode activesubstance, 5 g of carbon black (manufactured by Timcal, Super-P) as aconductive agent, 100 g of a 2% by mass aqueous solution ofcarboxymethyl cellulose sodium salt (manufactured by DKS Co. Ltd., tradename: Cellogen WS-C) as a thickener, and 6.7 g of a 30% by mass solutionof the polyurethane water dispersion 1D as a binder were mixed toprepare a positive electrode slurry having a solid content of 50%. Thepositive electrode slurry was coated on an aluminum foil having athickness of 20 μm with a coating machine, dried at 130° C., and thensubjected to a roll pressing treatment, thereby affording a positiveelectrode 1-5 having a positive electrode active substance in an amountof 22 mg/cm².

(Positive Electrode 1-6)

With a planetary mixer, 100 g of LiFePO₄ as a positive electrode activesubstance, 5 g of carbon black (manufactured by Timcal, Super-P) as aconductive agent, 6 g of polyvinylidene fluoride as a binder, and 135.7g of N-methyl-2-pyrrolidone as a dispersion medium were mixed to preparea positive electrode slurry having a solid content of 45%. The positiveelectrode slurry was applied by coating on an aluminum foil having athickness of 20 μm with a coating machine, dried at 130° C., and thensubjected to a roll pressing treatment, thereby affording a positiveelectrode 1-6 having a positive electrode active substance in an amountof 14.5 mg/cm².

(Positive Electrode 1-7)

With a planetary mixer, 100 g of LiFePO₄ as a positive electrode activesubstance, 5 g of carbon black (manufactured by Timcal, Super-P) as aconductive agent, 100 g of a 2% by mass aqueous solution ofcarboxymethyl cellulose sodium salt (manufactured by DKS Co. Ltd., tradename: Cellogen WS-C) as a thickener, and 6.7 g of a 30% by mass solutionof the polyurethane water dispersion 1D as a binder were mixed toprepare a positive electrode slurry having a solid content of 50%. Thepositive electrode slurry was coated on an aluminum foil having athickness of 20 μm with a coating machine, dried at 130° C., and thensubjected to a roll pressing treatment, thereby affording a positiveelectrode 1-7 having a positive electrode active substance in an amountof 14.5 mg/cm².

[Evaluation of Electrode]

The electrodes thus obtained were subjected to the followingevaluations. The evaluation results are shown in Table 3.

Evaluation of Bindability: The electrode obtained above was folded by180° with the coated surface directed outward and unfolded, and then thedegree of drop-off of the active substance on the coated surface (theproportion of the area of the drop-off portion with respect to thetotal) was visually judged.Evaluation Criteria

-   -   5: 0% drop-off    -   4: 25% drop-off    -   3: 50% drop-off    -   2: 75% drop-off    -   1: 100% drop-off        Evaluation of Resistance to Electrolytic Solution: The electrode        obtained above was immersed in a mixed solvent of EC (ethylene        carbonate)/PC (propylene carbonate)/DMC (dimethyl carbonate)/EMC        (ethyl methyl carbonate)/DEC (diethyl carbonate)=1/1/1/1/1 (vol)        at 60° C. for 7 days, and then the appearance of the coated film        was visually judged.        Evaluation Criteria    -   A: no change is observed on coated film    -   B: several blisters are formed on coated film    -   C: coated film is peeled off

TABLE 3 Evaluation Evaluation of of resistance Kind of electrodebindability electrolytic solution Ex. 1-1 Negative electrode 1-1 4 A Ex.1-2 Negative electrode 1-2 5 A Ex. 1-3 Negative electrode 1-3 4 A Ex.1-4 Negative electrode 1-4 4 A Ex. 1-5 Negative electrode 1-5 5 A Ex.1-6 Negative electrode 1-6 5 A Ex. 1-7 Negative electrode 1-7 5 A Ex.1-8 Negative electrode 1-8 4 A Ex. 1-9 Negative electrode 1-9 5 A Ex.1-10 Negative electrode 1-10 5 A Ex. 1-11 Negative electrode 1-11 4 AEx. 1-12 Negative electrode 1-17 4 A Ex. 1-13 Negative electrode 1-19 5A Ex. 1-14 Positive electrode 1-2 5 A Ex. 1-15 Positive electrode 1-5 4A Ex. 1-16 Positive electrode 1-7 5 A Comp. Ex. 1-1 Negative electrode1-12 3 B Comp. Ex. 1-2 Negative electrode 1-13 2 B Comp. Ex. 1-3Negative electrode 1-14 3 B Comp. Ex. 1-4 Negative electrode 1-15 3 AComp. Ex. 1-5 Negative electrode 1-16 3 A Comp. Ex. 1-6 Negativeelectrode 1-18 3 A Comp. Ex. 1-7 Negative electrode 1-20 3 A Comp. Ex.1-8 Positive electrode 1-1 3 A Comp. Ex. 1-9 Positive electrode 1-3 3 AComp. Ex. 1-10 Positive electrode 1-4 3 B Comp. Ex. 1-11 Positiveelectrode 1-6 3 A

The following will describe Examples in the case of containing, as the(B) component, a polycarbonate diol having the carbon number betweencarbonate bond chains of less than 6, together with ComparativeExamples.

[Synthesis of Polycarbonate Diol]

Synthetic Example 2-1 Synthesis of Polycarbonate Diol A

To a 500 ml separable flask equipped with a thermometer, a nitrogensealing tube and a stirrer were charged 177.1 g of diethyl carbonate and146.0 g of 1,3-propanediol, and tetra-n-butoxytitanium was added theretoas a catalyst so as to be a concentration of 100 ppm. Under a nitrogenflow, a transesterification reaction was carried out at 200° C. forabout 15 hours. Generated ethanol and excess diethyl carbonate wereremoved under reduced pressure, thereby affording a polycarbonate diol Ahaving a hydroxyl value of 56.2 mgKOH/g.

Synthetic Example 2-2 Synthesis of Polycarbonate Diol B

Production was performed in the same manner as in Synthetic Example 2-1except that 1,3-propanediol was changed to 73.0 g of 1,3-propanediol and73.0 g of 1,4-butanediol, thereby affording a polycarbonate diol Bhaving a hydroxyl value of 56.1 mgKOH/g which contains 1,3-propanedioland 1,4-butanediol as constituents.

Synthetic Example 2-3 Synthesis of Polycarbonate Diol C

Production was performed in the same manner as in Synthetic Example 2-1except that 1,3-propanediol was changed to 146.0 g of 1,4-butanediol,thereby affording a polycarbonate diol C having a hydroxyl value of 56.2mgKOH/g.

Synthetic Example 2-4 Synthesis of Polycarbonate Diol D

Production was performed in the same manner as in Synthetic Example 2-1except that 1,3-propanediol was changed to 73.0 g of 1,4-butanediol and84.3 g of 1,5-pentanediol, thereby affording a polycarbonate diol Dhaving a hydroxyl value of 37.5 mgKOH/g which contains 1,4-butanedioland 1,5-pentanediol as constituents.

Synthetic Example 2-5 Synthesis of Polycarbonate Diol E

Production was performed in the same manner as in Synthetic Example 2-1except that 1,3-propanediol was changed to 167.0 g of 1,5-pentanediol,thereby affording a polycarbonate diol E having a hydroxyl value of 37.4mgKOH/g.

Synthetic Example 2-6 Synthesis of Polycarbonate Diol F

Production was performed in the same manner as in Synthetic Example 2-1except that 1,3-propanediol was changed to 146.0 g of2-methyl-1,3-propanediol, thereby affording a polycarbonate diol Fhaving a hydroxyl value of 56.2 mgKOH/g.

Synthetic Example 2-7 Synthesis of Polycarbonate Diol G

Production was performed in the same manner as in Synthetic Example 2-1except that 1,3-propanediol was changed to 117.0 g of 1,4-butanediol and38.3 g of 1,6-hexanediol, thereby affording a polycarbonate diol Ghaving a hydroxyl value of 56.2 mgKOH/g which contains 1,4-butanedioland 1,6-hexanediol as constituents.

Synthetic Example 2-8 Synthesis of Polycarbonate Diol H

Production was performed in the same manner as in Synthetic Example 2-1except that 1,3-propanediol was changed to 192.0 g of 1,6-hexanediol,thereby affording a polycarbonate diol H having a hydroxyl value of 56.1mgKOH/g.

Synthetic Example 2-9 Synthesis of Polycarbonate Diol I

Production was performed in the same manner as in Synthetic Example 2-1except that 1,3-propanediol was changed to 260.0 g of 1,9-nonanediol,thereby affording a polycarbonate diol I having a hydroxyl value of 56.1mgKOH/g.

[Synthesis of Polyurethane Water Dispersion]

Synthetic Example 2-10 Synthesis of Polyurethane Water Dispersion 2A

To a four-neck flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen blowing tube were added 208.0 parts by massof a polycarbonate diol A, 3.0 parts by mass of trimethylolpropane(number of active hydrogen group: 3), 11.0 parts by mass ofdimethylolpropionic acid (number of active hydrogen group: 2), 78.0parts by mass of dicyclohexylmethane diisocyanate, and 200 parts by massof methyl ethyl ketone, and the reaction was carried out at 75° C. for 4hours to afford a methyl ethyl ketone solution of a urethane prepolymerhaving a free isocyanate group content of 2.0% with respect to thenonvolatile content. The solution was cooled to 45° C. and neutralizedby adding 8.3 parts by mass of triethylamine, and then emulsified anddispersed by using a homogenizer while gradually adding 900 parts bymass of water thereto. Subsequently, an aqueous solution obtained bydiluting 3.9 parts by mass of ethylenediamine (number of active hydrogengroup: 2) with 100 parts by mass of water was added thereto, and chainextending reaction was performed for 1 hour. The solvent was removedwhile heating at 50° C. under reduced pressure, thereby affording apolyurethane water dispersion 2A having a nonvolatile content of about30%.

Synthetic Example 2-11 Synthesis of Polyurethane Water Dispersion 2B

To a four-neck flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen blowing tube were added 206.4 parts by massof a polycarbonate diol B, 3.6 parts by mass of trimethylolpropane(number of active hydrogen group: 3), 13.0 parts by mass ofdimethylolpropionic acid (number of active hydrogen group: 2), 77.0parts by mass of dicyclohexylmethane diisocyanate, and 200 parts by massof methyl ethyl ketone, and the reaction was carried out at 75° C. for 4hours to afford a methyl ethyl ketone solution of a urethane prepolymerhaving a free isocyanate group content of 1.3% with respect to thenonvolatile content. The solution was cooled to 45° C. and neutralizedby adding 9.8 parts by mass of triethylamine, and then emulsified anddispersed by using a homogenizer while gradually adding 900 parts bymass of water thereto. Subsequently, an aqueous solution obtained bydiluting 2.5 parts by mass of ethylenediamine (number of active hydrogengroup: 2) with 100 parts by mass of water was added thereto, and chainextending reaction was performed for 1 hour. The solvent was removedwhile heating at 50° C. under reduced pressure, thereby affording apolyurethane water dispersion 2B having a nonvolatile content of about30%.

Synthetic Example 2-12 Synthesis of Polyurethane Water Dispersion 2C

To a four-neck flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen blowing tube were added 206.4 parts by massof a polycarbonate diol B, 3.6 parts by mass of trimethylolpropane(number of active hydrogen group: 3), 13.0 parts by mass ofdimethylolpropionic acid (number of active hydrogen group: 2), 77.0parts by mass of dicyclohexylmethane diisocyanate, and 200 parts by massof methyl ethyl ketone, and the reaction was carried out at 75° C. for 4hours to afford a methyl ethyl ketone solution of a urethane prepolymerhaving a free isocyanate group content of 1.3% with respect to thenonvolatile content. The solution was cooled to 45° C. and neutralizedby adding 9.8 parts by mass of triethylamine, and then emulsified anddispersed by using a homogenizer while gradually adding 900 parts bymass of water thereto. Subsequently, an aqueous solution obtained bydiluting 2.9 parts by mass of diethylenetriamine (number of activehydrogen group: 3) with 100 parts by mass of water was added thereto,and chain extending reaction was performed for 1 hour. The solvent wasremoved while heating at 50° C. under reduced pressure, therebyaffording a polyurethane water dispersion 2C having a nonvolatilecontent of about 30%.

Synthetic Example 2-13 Synthesis of Polyurethane Water Dispersion 2D

To a four-neck flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen blowing tube were added 205.5 parts by massof a polycarbonate diol C, 3.50 parts by mass of trimethylolpropane(number of active hydrogen group: 3), 12.0 parts by mass ofdimethylolpropionic acid (number of active hydrogen group: 2), 69.50parts by mass of dicyclohexylmethane diisocyanate, and 200 parts by massof methyl ethyl ketone, and the reaction was carried out at 75° C. for 4hours to afford a methyl ethyl ketone solution of a urethane prepolymerhaving a free isocyanate group content of 1.8% with respect to thenonvolatile content. The solution was cooled to 45° C. and neutralizedby adding 9.0 parts by mass of triethylamine, and then emulsified anddispersed by using a homogenizer while gradually adding 900 parts bymass of water thereto. Subsequently, an aqueous solution obtained bydiluting 3.5 parts by mass of ethylenediamine (number of active hydrogengroup: 2) with 100 parts by mass of water was added thereto, and chainextending reaction was performed for 1 hour. The solvent was removedwhile heating at 50° C. under reduced pressure, thereby affording apolyurethane water dispersion 2D having a nonvolatile content of about30%.

Synthetic Example 2-14 Synthesis of Polyurethane Water Dispersion 2E

To a four-neck flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen blowing tube were added 210.0 parts by massof a polycarbonate diol B, 3.50 parts by mass of trimethylolpropane(number of active hydrogen group: 3), 12.0 parts by mass ofdimethylolpropionic acid (number of active hydrogen group: 2), 74.5parts by mass of polymeric MDI, and 200 parts by mass of methyl ethylketone, and the reaction was carried out at 75° C. for 4 hours to afforda methyl ethyl ketone solution of a urethane prepolymer having a freeisocyanate group content of 1.6% with respect to the nonvolatilecontent. The solution was cooled to 45° C. and neutralized by adding 9.0parts by mass of triethylamine, and then emulsified and dispersed byusing a homogenizer while gradually adding 900 parts by mass of waterthereto. Subsequently, an aqueous solution obtained by diluting 3.1parts by mass of ethylenediamine (number of active hydrogen group: 2)with 100 parts by mass of water was added thereto, and chain extendingreaction was performed for 1 hour. The solvent was removed while heatingat 50° C. under reduced pressure, thereby affording a polyurethane waterdispersion 2E having a nonvolatile content of about 30%.

Synthetic Example 2-15 Synthesis of Polyurethane Water Dispersion 2F

To a four-neck flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen blowing tube were added 216.7 parts by massof a polycarbonate diol D, 3.30 parts by mass of trimethylolpropane(number of active hydrogen group: 3), 12.5 parts by mass ofdimethylolpropionic acid (number of active hydrogen group: 2), 67.50parts by mass of dicyclohexylmethane diisocyanate, and 200 parts by massof methyl ethyl ketone, and the reaction was carried out at 75° C. for 4hours to afford a methyl ethyl ketone solution of a urethane prepolymerhaving a free isocyanate group content of 1.4% with respect to thenonvolatile content. The solution was cooled to 45° C. and neutralizedby adding 9.4 parts by mass of triethylamine, and then emulsified anddispersed by using a homogenizer while gradually adding 900 parts bymass of water thereto. Subsequently, an aqueous solution obtained bydiluting 2.7 parts by mass of ethylenediamine (number of active hydrogengroup: 2) with 100 parts by mass of water was added thereto, and chainextending reaction was performed for 1 hour. The solvent was removedwhile heating at 50° C. under reduced pressure, thereby affording apolyurethane water dispersion 2F having a nonvolatile content of about30%.

Synthetic Example 2-16 Synthesis of Polyurethane Water Dispersion 2G

To a four-neck flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen blowing tube were added 216.7 parts by massof a polycarbonate diol E, 3.30 parts by mass of trimethylolpropane(number of active hydrogen group: 3), 12.5 parts by mass ofdimethylolpropionic acid (number of active hydrogen group: 2), 67.50parts by mass of dicyclohexylmethane diisocyanate, and 200 parts by massof methyl ethyl ketone, and the reaction was carried out at 75° C. for 4hours to afford a methyl ethyl ketone solution of a urethane prepolymerhaving a free isocyanate group content of 1.4% with respect to thenonvolatile content. The solution was cooled to 45° C. and neutralizedby adding 9.4 parts by mass of triethylamine, and then emulsified anddispersed by using a homogenizer while gradually adding 900 parts bymass of water thereto. Subsequently, an aqueous solution obtained bydiluting 2.7 parts by mass of ethylenediamine (number of active hydrogengroup: 2) with 100 parts by mass of water was added thereto, and chainextending reaction was performed for 1 hour. The solvent was removedwhile heating at 50° C. under reduced pressure, thereby affording apolyurethane water dispersion 2G having a nonvolatile content of about30%.

Synthetic Example 2-17 Synthesis of Polyurethane Water Dispersion 2H

To a four-neck flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen blowing tube were added 205.5 parts by massof a polycarbonate diol F, 3.50 parts by mass of trimethylolpropane(number of active hydrogen group: 3), 12.0 parts by mass ofdimethylolpropionic acid (number of active hydrogen group: 2), 79.0parts by mass of dicyclohexylmethane diisocyanate, and 200 parts by massof methyl ethyl ketone, and the reaction was carried out at 75° C. for 4hours to afford a methyl ethyl ketone solution of a urethane prepolymerhaving a free isocyanate group content of 1.6% with respect to thenonvolatile content. The solution was cooled to 45° C. and neutralizedby adding 9.0 parts by mass of triethylamine, and then emulsified anddispersed by using a homogenizer while gradually adding 900 parts bymass of water thereto. Subsequently, an aqueous solution obtained bydiluting 3.5 parts by mass of ethylenediamine (number of active hydrogengroup: 2) with 100 parts by mass of water was added thereto, and chainextending reaction was performed for 1 hour. The solvent was removedwhile heating at 50° C. under reduced pressure, thereby affording apolyurethane water dispersion 2H having a nonvolatile content of about30%.

Synthetic Example 2-18 Synthesis of Polyurethane Water Dispersion 2I

To a four-neck flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen blowing tube were added 174.0 parts by massof a polycarbonate diol F, 8.0 parts by mass of trimethylolpropane(number of active hydrogen group: 3), 12.0 parts by mass ofdimethylolpropionic acid (number of active hydrogen group: 2), 79.0parts by mass of dicyclohexylmethane diisocyanate, and 200 parts by massof methyl ethyl ketone, and the reaction was carried out at 75° C. for 4hours to afford a methyl ethyl ketone solution of a urethane prepolymerhaving a free isocyanate group content of 3.7% with respect to thenonvolatile content. The solution was cooled to 45° C. and neutralizedby adding 9.0 parts by mass of triethylamine, and then emulsified anddispersed by using a homogenizer while gradually adding 900 parts bymass of water thereto. Subsequently, an aqueous solution obtained bydiluting 8.2 parts by mass of diethylenetriamine (number of activehydrogen group: 2) with 100 parts by mass of water was added thereto,and chain extending reaction was performed for 1 hour. The solvent wasremoved while heating at 50° C. under reduced pressure, therebyaffording a polyurethane water dispersion 2I having a nonvolatilecontent of about 30%.

Synthetic Example 2-19 Synthesis of Polyurethane Water Dispersion 2J

To a four-neck flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen blowing tube were added 235.0 parts by massof a polycarbonate diol C, 3.0 parts by mass of trimethylolpropane(number of active hydrogen group: 3), 12.0 parts by mass ofdimethylolpropionic acid (number of active hydrogen group: 2), 50.00parts by mass of hexamethylene diisocyanate, and 200 parts by mass ofmethyl ethyl ketone, and the reaction was carried out at 75° C. for 4hours to afford a methyl ethyl ketone solution of a urethane prepolymerhaving a free isocyanate group content of 1.4% with respect to thenonvolatile content. The solution was cooled to 45° C. and neutralizedby adding 9.0 parts by mass of triethylamine, and then emulsified anddispersed by using a homogenizer while gradually adding 900 parts bymass of water thereto. Subsequently, an aqueous solution obtained bydiluting 2.7 parts by mass of ethylenediamine (number of active hydrogengroup: 2) with 100 parts by mass of water was added thereto, and chainextending reaction was performed for 1 hour. The solvent was removedwhile heating at 50° C. under reduced pressure, thereby affording apolyurethane water dispersion 2J having a nonvolatile content of about30%.

Synthetic Example 2-20 Synthesis of Polyurethane Water Dispersion 2K

To a four-neck flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen blowing tube were added 208.7 parts by massof a polycarbonate diol G, 3.3 parts by mass of trimethylolpropane(number of active hydrogen group: 3), 12.0 parts by mass ofdimethylolpropionic acid (number of active hydrogen group: 2), 76.0parts by mass of hexamethylene diisocyanate, and 200 parts by mass ofmethyl ethyl ketone, and the reaction was carried out at 75° C. for 4hours to afford a methyl ethyl ketone solution of a urethane prepolymerhaving a free isocyanate group content of 1.4% with respect to thenonvolatile content. The solution was cooled to 45° C. and neutralizedby adding 9.0 parts by mass of triethylamine, and then emulsified anddispersed by using a homogenizer while gradually adding 900 parts bymass of water thereto. Subsequently, an aqueous solution obtained bydiluting 2.9 parts by mass of ethylenediamine (number of active hydrogengroup: 2) with 100 parts by mass of water was added thereto, and chainextending reaction was performed for 1 hour. The solvent was removedwhile heating at 50° C. under reduced pressure, thereby affording apolyurethane water dispersion 2K having a nonvolatile content of about30%.

Synthetic Example 2-21 Synthesis of Polyurethane Water Dispersion 2L

To a four-neck flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen blowing tube were added 239.8 parts by massof a polycarbonate diol H, 0.30 parts by mass of trimethylolpropane(number of active hydrogen group: 3), 12.0 parts by mass ofdimethylolpropionic acid (number of active hydrogen group: 2), 47.90parts by mass of hexamethylene diisocyanate, and 200 parts by mass ofmethyl ethyl ketone, and the reaction was carried out at 75° C. for 4hours to afford a methyl ethyl ketone solution of a urethane prepolymerhaving a free isocyanate group content of 1.8% with respect to thenonvolatile content. The solution was cooled to 45° C. and neutralizedby adding 9.0 parts by mass of triethylamine, and then emulsified anddispersed by using a homogenizer while gradually adding 900 parts bymass of water thereto. Subsequently, an aqueous solution obtained bydiluting 3.5 parts by mass of ethylenediamine (number of active hydrogengroup: 2) with 100 parts by mass of water was added thereto, and chainextending reaction was performed for 1 hour. The solvent was removedwhile heating at 50° C. under reduced pressure, thereby affording apolyurethane water dispersion 2L having a nonvolatile content of about30%.

Synthetic Example 2-22 Synthesis of Polyurethane Water Dispersion 2M

To a four-neck flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen blowing tube were added 195.7 parts by massof a polycarbonate diol H, 12.3 parts by mass of trimethylolpropane(number of active hydrogen group: 3), 12.0 parts by mass ofdimethylolpropionic acid (number of active hydrogen group: 2), 80.0parts by mass of hexamethylene diisocyanate, and 200 parts by mass ofmethyl ethyl ketone, and the reaction was carried out at 75° C. for 4hours to afford a methyl ethyl ketone solution of a urethane prepolymerhaving a free isocyanate group content of 4.0% with respect to thenonvolatile content. The solution was cooled to 45° C. and neutralizedby adding 9.0 parts by mass of triethylamine, and then emulsified anddispersed by using a homogenizer while gradually adding 900 parts bymass of water thereto. Subsequently, an aqueous solution obtained bydiluting 8.8 parts by mass of ethylenediamine (number of active hydrogengroup: 2) with 100 parts by mass of water was added thereto, and chainextending reaction was performed for 1 hour. The solvent was removedwhile heating at 50° C. under reduced pressure, thereby affording apolyurethane water dispersion 2M having a nonvolatile content of about30%.

Synthetic Example 2-23 Synthesis of Polyurethane Water Dispersion 2N

To a four-neck flask equipped with a stirrer, a reflux condenser, athermometer, and a nitrogen blowing tube were added 240.0 parts by massof a polycarbonate diol I, 12.0 parts by mass of dimethylolpropionicacid (number of active hydrogen group: 2), 48.00 parts by mass ofhexamethylene diisocyanate, and 200 parts by mass of methyl ethylketone, and the reaction was carried out at 75° C. for 4 hours to afforda methyl ethyl ketone solution of a urethane prepolymer having a freeisocyanate group content of 1.9% with respect to the nonvolatilecontent. The solution was cooled to 45° C. and neutralized by adding 9.0parts by mass of triethylamine, and then emulsified and dispersed byusing a homogenizer while gradually adding 900 parts by mass of waterthereto. Subsequently, an aqueous solution obtained by diluting 3.7parts by mass of ethylenediamine (number of active hydrogen group: 2)with 100 parts by mass of water was added thereto, and chain extendingreaction was performed for 1 hour. The solvent was removed while heatingat 50° C. under reduced pressure, thereby affording a polyurethane waterdispersion 2N having a nonvolatile content of about 30%.

[Evaluation of Polyurethane Water Dispersion]

The polyurethane water dispersions obtained as described above weresubjected to the following measurements. The results are shown in Table4.

Weight of the nonvolatile content of the polyurethane water dispersion:Measured in accordance with JIS K 6828.

Crosslinking density in the resin solid content of the polyurethanewater dispersion: Calculated according to the Mathematical Expression 1shown above.

Acid value of the polyurethane resin: Measured in accordance with JIS K0070-1992.

Carbonate bond equivalent, urea bond equivalent and urethane bondequivalent: Calculated according to the Mathematical Expression 2,Mathematical Expression 3 and Mathematical Expression 4, respectively.

Measurement of average particle diameter of the polyurethane waterdispersion: The average particle diameter was measured with MicrotracUPA-UZ152 (manufactured by Nikkiso Co., Ltd.), and a 50% average valuewas calculated as the average particle diameter.

TABLE 4 Average Urethane Carbonate Polyurethane particle bond Urea bondbond water Crosslinking diameter Acid value equivalent equivalentequivalent dispersion density (μm) (mgKOH/g) (g/eq) (g/eq) (g/eq) 2A0.07 0.02 15 674 2106 149 2B 0.09 0.02 18 614 3180 160 2C 0.18 0.03 18615 3186 160 2D 0.09 0.03 16 632 2364 171 2E 0.09 0.02 16 632 2610 1582F 0.08 0.02 17 725 3086 168 2G 0.08 0.04 17 725 3086 182 2H 0.09 0.0216 632 2364 171 2I 0.45 0.03 16 568 1154 205 2J 0.07 0.05 16 612 3030149 2K 0.08 0.03 16 639 2853 177 2L 0.007 0.02 16 691 2326 182 2M 0.570.02 16 467 1065 227 2N 0 0.03 16 702 2200 235[Production of Electrode]

The binders used for production of electrodes are shown in Table 5below.

TABLE 5 Kind of electrode Kind of binder Negative electrode 2-1Polyurethane water dispersion 2A Negative electrode 2-2 Polyurethanewater dispersion 2B Negative electrode 2-3 Polyurethane water dispersion2C Negative electrode 2-4 Polyurethane water dispersion 2D Negativeelectrode 2-5 Polyurethane water dispersion 2E Negative electrode 2-6Polyurethane water dispersion 2F Negative electrode 2-7 Polyurethanewater dispersion 2G Negative electrode 2-8 Polyurethane water dispersion2H Negative electrode 2-9 Polyurethane water dispersion 2I Negativeelectrode 2-10 Polyurethane water dispersion 2J Negative electrode 2-11Polyurethane water dispersion 2K Negative electrode 2-12 Polyurethanewater dispersion 2L Negative electrode 2-13 Polyurethane waterdispersion 2M Negative electrode 2-14 Polyurethane water dispersion 2NNegative electrode 2-15 SBR Negative electrode 2-16 Polyurethane waterdispersion 2C Negative electrode 2-17 SBR Negative electrode 2-18Polyurethane water dispersion 2H Negative electrode 2-19 SBR Positiveelectrode 2-1 Polyvinylidene fluoride Positive electrode 2-2Polyurethane water dispersion 2B Positive electrode 2-3 Polyurethanewater dispersion 2M Positive electrode 2-4 Polyvinylidene fluoridePositive electrode 2-5 Polyurethane water dispersion 2F Positiveelectrode 2-6 Polyvinylidene fluoride Positive electrode 2-7Polyurethane water dispersion 2H[Production of Negative Electrode](Negative Electrode 2-1)

With a planetary mixer, 100 g of natural graphite as a negativeelectrode active substance, 0.5 g of carbon black (manufactured byTimcal, Super-P) as a conductive agent, 100 g of a 2% by mass aqueoussolution of carboxymethyl cellulose sodium salt (manufactured by DKS Co.Ltd., trade name: Cellogen WS-C) as a thickener, and 6.7 g of a 30% bymass solution of the polyurethane water dispersion 2A as a binder weremixed to prepare a negative electrode slurry having a solid content of50%. The negative electrode slurry was applied by coating on anelectrolytic copper foil having a thickness of 10 μm with a coatingmachine, dried at 120° C., and then subjected to a roll pressingtreatment, thereby affording a negative electrode 2-1 having a negativeelectrode active substance in an amount of 7 mg/cm².

(Negative Electrodes 2-2 to 2-15)

Negative electrodes 2-2 to 2-15 were produced in the same manner as inthe negative electrode 2-1 except that the polyurethane water dispersion2A was changed to the polyurethane water dispersions or SBR shown inTable 5.

(Negative Electrode 2-16)

With a planetary mixer, 100 g of SiO (average particle diameter: 4.5 μm,specific surface area: 5.5 m²/g) as a negative electrode activesubstance, 5 g of carbon black (manufactured by Timcal, Super-P) as aconductive agent, 100 g of a 2% by mass aqueous solution ofcarboxymethyl cellulose sodium salt (manufactured by DKS Co. Ltd., tradename: Cellogen WS-C) as a thickener, and 6.7 g of a 30% by mass solutionof the polyurethane water dispersion 2C as a binder were mixed toprepare a negative electrode slurry having a solid content of 50%. Thenegative electrode slurry was applied by coating on an electrolyticcopper foil having a thickness of 10 μm with a coating machine, dried at120° C., and then subjected to a roll pressing treatment, therebyaffording a negative electrode 2-16 having a negative electrode activesubstance in an amount of 2.5 mg/cm².

(Negative Electrode 2-17)

A negative electrode 2-16 was produced in the same manner as in thenegative electrode 16 except that the polyurethane water dispersion 2Cwas changed to SBR.

(Negative Electrode 2-18)

With a planetary mixer, 100 g of Li₄Ti₅O₁₂ as a negative electrodeactive substance, 5 g of carbon black (manufactured by Timcal, Super-P)as a conductive agent, 100 g of a 2% by mass aqueous solution ofcarboxymethyl cellulose sodium salt (manufactured by DKS Co. Ltd., tradename: Cellogen WS-C) as a thickener, and 6.7 g of a 30% by mass solutionof the polyurethane water dispersion 2H as a binder were mixed toprepare a negative electrode slurry having a solid content of 50%. Thenegative electrode slurry was applied by coating on an electrolyticcopper foil having a thickness of 10 μm with a coating machine, dried at120° C., and then subjected to a roll pressing treatment, therebyaffording a negative electrode 2-18 having a negative electrode activesubstance in an amount of 9.7 mg/cm².

(Negative Electrode 2-19)

A negative electrode 2-19 was produced in the same manner as in thenegative electrode 2-18 except that the polyurethane water dispersion 2Hwas changed to SBR.

[Production of Positive Electrode]

(Positive Electrode 2-1)

With a planetary mixer, 100 g of LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂ as apositive electrode active substance, 7.8 g of carbon black (manufacturedby Timcal, Super-P) as a conductive agent, 6 g of polyvinylidenefluoride as a binder, and 61.3 g of N-methyl-2-pyrrolidone as adispersion medium were mixed to prepare a positive electrode slurryhaving a solid content of 65%. The positive electrode slurry was appliedby coating on an aluminum foil having a thickness of 20 μm with acoating machine, dried at 130° C., and then subjected to a roll pressingtreatment, thereby affording a positive electrode 2-1 having a positiveelectrode active substance in an amount of 13.8 mg/cm².

(Positive Electrodes 2-2 and 2-3)

With a planetary mixer, 100 g of LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂ as apositive electrode active substance, 7.8 g of carbon black (manufacturedby Timcal, Super-P) as a conductive agent, 100 g of a 2% by mass aqueoussolution of carboxymethyl cellulose sodium salt (manufactured by DKS Co.Ltd., trade name: Cellogen WS-C) as a thickener, and 6.7 g of a 30% bymass solution of each of the polyurethane water dispersions shown inTable 5 as a binder were mixed to prepare a positive electrode slurryhaving a solid content of 50%. The positive electrode slurry was appliedby coating on an aluminum foil having a thickness of 20 μm with acoating machine, dried at 130° C., and then subjected to a roll pressingtreatment, thereby affording positive electrodes 2-2 and 2-3 each havinga positive electrode active substance in an amount of 13.8 mg/cm².

(Positive Electrode 2-4)

With a planetary mixer, 100 g of LiMn₂O₄ as a positive electrode activesubstance, 5 g of carbon black (manufactured by Timcal, Super-P) as aconductive agent, 6 g of polyvinylidene fluoride as a binder, and 59.8 gof N-methyl-2-pyrrolidone as a dispersion medium were mixed to prepare apositive electrode slurry having a solid content of 65%. The positiveelectrode slurry was applied by coating on an aluminum foil having athickness of 20 μm with a coating machine, dried at 130° C., and thensubjected to a roll pressing treatment, thereby affording a positiveelectrode 2-4 having a positive electrode active substance in an amountof 22 mg/cm².

(Positive Electrode 2-5)

With a planetary mixer, 100 g of LiMn₂O₄ as a positive electrode activesubstance, 5 g of carbon black (manufactured by Timcal, Super-P) as aconductive agent, 100 g of a 2% by mass aqueous solution ofcarboxymethyl cellulose sodium salt (manufactured by DKS Co. Ltd., tradename: Cellogen WS-C) as a thickener, and 6.7 g of a 30% by mass solutionof the polyurethane water dispersion 2F as a binder were mixed toprepare a positive electrode slurry having a solid content of 50%. Thepositive electrode slurry was applied by coating on an aluminum foilhaving a thickness of 20 μm with a coating machine, dried at 130° C.,and then subjected to a roll pressing treatment, thereby affording apositive electrode 2-5 having a positive electrode active substance inan amount of 22 mg/cm².

(Positive Electrode 2-6)

With a planetary mixer, 100 g of LiFePO₄ as a positive electrode activesubstance, 5 g of carbon black (manufactured by Timcal, Super-P) as aconductive agent, 6 g of polyvinylidene fluoride as a binder, and 135.7g of N-methyl-2-pyrrolidone as a dispersion medium were mixed to preparea positive electrode slurry having a solid content of 45%. The positiveelectrode slurry was applied by coating on an aluminum foil having athickness of 20 μm with a coating machine, dried at 130° C., and thensubjected to a roll pressing treatment, thereby affording a positiveelectrode 2-6 having a positive electrode active substance in an amountof 14.5 mg/cm².

(Positive Electrode 2-7)

With a planetary mixer, 100 g of LiFePO₄ as a positive electrode activesubstance, 5 g of carbon black (manufactured by Timcal, Super-P) as aconductive agent, 100 g of a 2% by mass aqueous solution ofcarboxymethyl cellulose sodium salt (manufactured by DKS Co. Ltd., tradename: Cellogen WS-C) as a thickener, and 6.7 g of a 30% by mass solutionof the polyurethane water dispersion 2H as a binder were mixed toprepare a positive electrode slurry having a solid content of 50%. Thepositive electrode slurry was applied by coating on an aluminum foilhaving a thickness of 20 μm with a coating machine, dried at 130° C.,and then subjected to a roll pressing treatment, thereby affording apositive electrode 2-7 having a positive electrode active substance inan amount of 14.5 mg/cm².

[Evaluation of Electrode]

The electrodes thus obtained were subjected to the evaluation ofbindability according to the same method as described above. Theevaluation results are shown in Table 6.

TABLE 6 Evaluation of Kind of electrode bindability Ex. 2-1 Negativeelectrode 2-1 4 Ex. 2-2 Negative electrode 2-2 5 Ex. 2-3 Negativeelectrode 2-3 4 Ex. 2-4 Negative electrode 2-4 5 Ex. 2-5 Negativeelectrode 2-5 4 Ex. 2-6 Negative electrode 2-6 5 Ex. 2-7 Negativeelectrode 2-7 5 Ex. 2-8 Negative electrode 2-8 4 Ex. 2-9 Negativeelectrode 2-9 5 Ex. 2-10 Negative electrode 2-10 4 Ex. 2-11 Negativeelectrode 2-11 4 Ex. 2-12 Negative electrode 2-16 5 Ex. 2-13 Negativeelectrode 2-18 4 Ex. 2-14 Positive electrode 2-2 4 Ex. 2-15 Positiveelectrode 2-4 5 Ex. 2-16 Positive electrode 2-6 5 Comp. Ex. 2-1 Negativeelectrode 2-12 3 Comp. Ex. 2-2 Negative electrode 2-13 2 Comp. Ex. 2-3Negative electrode 2-14 3 Comp. Ex. 2-4 Negative electrode 2-15 3 Comp.Ex. 2-5 Negative electrode 2-17 3 Comp. Ex. 2-6 Negative electrode 2-193 Comp. Ex. 2-7 Positive electrode 2-1 3 Comp. Ex. 2-8 Positiveelectrode 2-3 3 Comp. Ex. 2-9 Positive electrode 2-4 3 Comp. Ex. 2-10Positive electrode 2-6 3[Production of Lithium Secondary Battery]

The positive electrode and the negative electrode obtained as describedabove were combined as shown in Tables 7 and 8 below and laminated oneach other with a polyolefinic (PE/PP) separator as a separatorintervening between the electrodes, and a positive electrode terminaland a negative electrode terminal were ultrasonic-welded to the positiveand negative electrodes, respectively. The laminate was placed in analuminum-laminated package, which was then heat-sealed while leaving anopening for injecting a liquid. Thus, there was produced a batterybefore liquid injection, which had a positive electrode area of 18 cm²and a negative electrode area of 19.8 cm². Thereinto was charged anelectrolytic solution containing LiPF₆ (1.0 mol/L) dissolved in a mixedsolvent of ethylene carbonate and diethyl carbonate (30/70 in volumeratio), and the opening was heat-sealed, thereby affording a battery forevaluation.

TABLE 7 Constitution of electrodes Negative electrode Positive electrodeEx. 1-17 Negative electrode 1-1 Positive electrode 1-1 Ex. 1-18 Negativeelectrode 1-2 Positive electrode 1-1 Ex. 1-19 Negative electrode 1-3Positive electrode 1-1 Ex. 1-20 Negative electrode 1-4 Positiveelectrode 1-1 Ex. 1-21 Negative electrode 1-5 Positive electrode 1-1 Ex.1-22 Negative electrode 1-6 Positive electrode 1-1 Ex. 1-23 Negativeelectrode 1-7 Positive electrode 1-1 Ex. 1-24 Negative electrode 1-8Positive electrode 1-1 Ex. 1-25 Negative electrode 1-9 Positiveelectrode 1-1 Ex. 1-26 Negative electrode 1-10 Positive electrode 1-1Ex. 1-27 Negative electrode 1-11 Positive electrode 1-1 Ex. 1-28Negative electrode 1-17 Positive electrode 1-1 Ex. 1-29 Negativeelectrode 1-19 Positive electrode 1-1 Ex. 1-30 Negative electrode 1-16Positive electrode 1-2 Ex. 1-31 Negative electrode 1-16 Positiveelectrode 1-5 Ex. 1-32 Negative electrode 1-16 Positive electrode 1-7Ex. 1-33 Negative electrode 1-2 Positive electrode 1-2 Comp. Ex. 1-12Negative electrode 1-12 Positive electrode 1-1 Comp. Ex. 1-13 Negativeelectrode 1-13 Positive electrode 1-1 Comp. Ex. 1-14 Negative electrode1-14 Positive electrode 1-1 Comp. Ex. 1-15 Negative electrode 1-15Positive electrode 1-1 Comp. Ex. 1-16 Negative electrode 1-16 Positiveelectrode 1-1 Comp. Ex. 1-17 Negative electrode 1-18 Positive electrode1-1 Comp. Ex. 1-18 Negative electrode 1-20 Positive electrode 1-1 Comp.Ex. 19 Negative electrode 1-16 Positive electrode 1-3 Comp. Ex. 20Negative electrode 1-16 Positive electrode 1-4 Comp. Ex. 21 Negativeelectrode 1-16 Positive electrode 1-6

TABLE 8 Constitution of electrodes Negative electrode Positive electrodeEx. 2-17 Negative electrode 2-1 Positive electrode 2-1 Ex. 2-18 Negativeelectrode 2-2 Positive electrode 2-1 Ex. 2-19 Negative electrode 2-3Positive electrode 2-1 Ex. 2-20 Negative electrode 2-4 Positiveelectrode 2-1 Ex. 2-21 Negative electrode 2-5 Positive electrode 2-1 Ex.2-22 Negative electrode 2-6 Positive electrode 2-1 Ex. 2-23 Negativeelectrode 2-7 Positive electrode 2-1 Ex. 2-24 Negative electrode 2-8Positive electrode 2-1 Ex. 2-25 Negative electrode 2-9 Positiveelectrode 2-1 Ex. 2-26 Negative electrode 2-10 Positive electrode 2-1Ex. 2-27 Negative electrode 2-11 Positive electrode 2-1 Ex. 2-28Negative electrode 2-16 Positive electrode 2-1 Ex. 2-29 Negativeelectrode 2-18 Positive electrode 2-1 Ex. 2-30 Negative electrode 2-15Positive electrode 2-2 Ex. 2-31 Negative electrode 2-15 Positiveelectrode 2-5 Ex. 2-32 Negative electrode 2-15 Positive electrode 2-7Ex. 2-33 Negative electrode 2-2 Positive electrode 2-2 Comp. Ex. 2-11Negative electrode 2-12 Positive electrode 2-1 Comp. Ex. 2-12 Negativeelectrode 2-13 Positive electrode 2-1 Comp. Ex. 2-13 Negative electrode2-14 Positive electrode 2-1 Comp. Ex. 2-14 Negative electrode 2-15Positive electrode 2-1 Comp. Ex. 2-15 Negative electrode 2-17 Positiveelectrode 2-1 Comp. Ex. 2-16 Negative electrode 2-19 Positive electrode2-1 Comp. Ex. 2-17 Negative electrode 2-15 Positive electrode 2-3 Comp.Ex. 2-18 Negative electrode 2-15 Positive electrode 2-4 Comp. Ex. 2-19Negative electrode 2-15 Positive electrode 2-6[Evaluation of Battery Performance]

The lithium secondary batteries thus produced were subjected to aperformance test at 20° C. The test method was as follows. The testresults are shown in Tables 9 and 10.

(Cell Impedance)

For the cell impedance, a resistance value at a frequency of 1 kHz wasmeasured by using an impedance analyzer (manufactured by ZAHNER).

(Charge and Discharge Cycle Characteristics)

The charge and discharge cycle characteristics were measured under thefollowing conditions.

In the case where LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂ or LiMn₂O₄ was used asthe positive electrode active substance and natural graphite was used asthe negative electrode active substance, a cycle in which CC (constantcurrent) charging was conducted until 4.2 V at a current densitycorresponding to 1 C, subsequently switched to CV (constant voltage)charging at 4.2 V and a charging was conducted for 1.5 hours, and thenCC discharging was conducted until 2.7 V at a current densitycorresponding to 1 C, was performed for 300 cycles at 20° C. The ratioof the 1 C discharge capacity after the 300 cycles with respect to theinitial 1 C discharge capacity was designated as a 1 C charge anddischarge cycle retention rate.

In the case where LiFePO₄ was used as the positive electrode activesubstance and natural graphite was used as the negative electrode activesubstance, a cycle in which CC (constant current) charging was conducteduntil 4.0 V at a current density corresponding to 1 C, subsequentlyswitched to CV (constant voltage) charging at 4.0 V and a charging wasconducted for 1.5 hours, and then CC discharging was conducted until 2.0V at a current density corresponding to 1 C, was performed for 300cycles at 20° C. The ratio of the 1 C discharge capacity after the 300cycles with respect to the initial 1 C discharge capacity was designatedas a 1 C charge and discharge cycle retention rate.

In the case where LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂ was used as the positiveelectrode active substance and Li₄Ti₅O₁₂ was used as the negativeelectrode active substance, a cycle in which CC (constant current)charging was conducted until 2.9 V at a current density corresponding to1 C, subsequently switched to CV (constant voltage) charging at 2.9 Vand a charging was conducted for 1.5 hours, and then CC discharging wasconducted until 1.0 V at a current density corresponding to 1 C, wasperformed for 300 cycles at 20° C. The ratio of the 1 C dischargecapacity after the 300 cycles with respect to the initial 1 C dischargecapacity was designated as a 1 C charge and discharge cycle retentionrate.

In the case where LiNi_(1/3)Co_(1/3)Mn_(1/3)O₂ was used as the positiveelectrode active substance and SiO was used as the negative electrodeactive substance, a cycle in which CC (constant current) charging wasconducted until 4.2 V at a current density corresponding to 1 C,subsequently switched to CV (constant voltage) charging at 4.2 V and acharging was conducted for 1.5 hours, and then CC discharging wasconducted until 2.7 V at a current density corresponding to 1 C, wasperformed for 50 cycles at 20° C. The ratio of the 1 C dischargecapacity after the 50 cycles with respect to the initial 1 C dischargecapacity was designated as a 1 C charge and discharge cycle retentionrate.

TABLE 9 Evaluation of battery Capacity retention rate Cell impedanceafter charge and discharge (mΩ/1 kHz) cycle characteristics (%) Ex. 1-17185 96 Ex. 1-18 180 97 Ex. 1-19 200 94 Ex. 1-20 192 96 Ex. 1-21 196 95Ex. 1-22 198 96 Ex. 1-23 198 95 Ex. 1-24 185 97 Ex. 1-25 189 96 Ex. 1-26188 96 Ex. 1-27 192 96 Ex. 1-28 201 95 Ex. 1-29 184 97 Ex. 1-30 197 96Ex. 1-31 201 94 Ex. 1-32 187 97 Ex. 1-33 188 97 Comp. Ex. 1-12 390 50 orlower Comp. Ex. 1-13 350 71 Comp. Ex. 1-14 310 79 Comp. Ex. 1-15 265 84Comp. Ex. 1-16 245 86 Comp. Ex. 1-17 278 80 Comp. Ex. 1-18 245 88 Comp.Ex. 1-19 293 76 Comp. Ex. 1-20 250 89 Comp. Ex. 1-21 254 88

TABLE 10 Evaluation of battery Capacity retention rate Cell impedanceafter charge and discharge (mΩ/1 kHz) cycle characteristics (%) Ex. 2-17195 95 Ex. 2-18 197 96 Ex. 2-19 201 96 Ex. 2-20 190 96 Ex. 2-21 200 95Ex. 2-22 202 95 Ex. 2-23 198 96 Ex. 2-24 195 97 Ex. 2-25 198 96 Ex. 2-26190 96 Ex. 2-27 201 95 Ex. 2-28 210 93 Ex. 2-29 195 97 Ex. 2-30 209 94Ex. 2-31 206 95 Ex. 2-32 188 96 Ex. 2-33 191 97 Comp. Ex. 2-11 360 50 orlower Comp. Ex. 2-12 280 82 Comp. Ex. 2-13 320 70 Comp. Ex. 2-14 238 88Comp. Ex. 2-15 254 82 Comp. Ex. 2-16 230 89 Comp. Ex. 2-17 303 72 Comp.Ex. 2-18 230 88 Comp. Ex. 2-19 226 89

It is understood from Tables 9 and 10 that, as compared to the use ofconventionally used styrene-butadiene rubber or polyvinylidene fluoride,the use of the polyurethane water dispersions of the present inventionprovides more excellent bindability, lower cell impedance, and higherretention of capacity retention rate after the cycle characteristics.

INDUSTRIAL APPLICABILITY

The binder of the present invention can be utilized as a binder for anelectrode of a lithium secondary battery, and an electrode producedtherewith may be used for production of various lithium secondarybatteries. The resulting lithium secondary batteries can be used invarious portable equipments, such as a mobile phone, a notebook personalcomputer, a personal digital assistant (PDA), a video camera, and adigital camera, and also as a medium-sized or large-sized lithiumsecondary battery to be mounted on an electric power-assisted bicycle,an electrically powered automobile and the like.

The invention claimed is:
 1. A binder for an electrode of a lithiumsecondary battery, comprising a water dispersion of a polyurethaneformed of (A) a polyisocyanate that contains an alicyclic isocyanateand/or an aromatic isocyanate, (B) a compound having two or more activehydrogen groups comprising 50% by mass or more and 90% by mass or lesswith respect to the polyurethane of a polycarbonate diol having a carbonnumber between carbonate bond chains of less than 6, and optionally, anolefinic polyol, (C) a compound having one or more active hydrogengroups and a hydrophilic group, and (D) a chain extending agent, whereinthe polyurethane has a crosslinking density of 0.01 or more and 0.50 orless per 1,000 molecular weight of the polyurethane.
 2. The binder foran electrode of a lithium secondary battery according to claim 1,wherein the polyurethane has a urethane bond equivalent of 200 g/eq ormore and 2,000 g/eq or less.
 3. The binder for an electrode of a lithiumsecondary battery according to claim 1, wherein the olefinic polyolcontained as the (B) component is one kind or two or more kinds selectedfrom polybutadiene polyol, polyisoprene polyol, hydrogenatedpolybutadiene polyol, and hydrogenated polyisoprene polyol.
 4. Thebinder for an electrode of a lithium secondary battery according toclaim 1, wherein the (C) compound having one or more active hydrogengroups and a hydrophilic group contains a carboxyl group as thehydrophilic group.
 5. An electrode produced by using the binder for anelectrode of a lithium secondary battery described in claim
 1. 6. Alithium secondary battery comprising the electrode described in claim 5.